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Building H-Bridges 

• Robotic Arms and Grippers 

• Beyond Bleeps and Bloops 


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Autonomous Robots and 
Multiple Sensors 

by Bryan Bergeron 

Part 1: Fusion Fundamentals 

Features & Projects 

36 Mobility to the Maxx 

by Chris Cooper^***^ 
Part 4: A Sense of Direction. 

40 Power Tool Drag Racing 

by Simone Davalos 

Tim the Toolman meets Jeff Gordan 



Ruilding (H-)Bridges 

by Peter Best 

Learn how to build electronic circuitry 
that controls myriad functions within 
a motor's magnetic domain. 

The Combat Zone 

SERVO Magazine (ISSN I546-0592/CDN Pub Agree#40702530) is published monthly for $24.95 per year byT & L Publications, Inc., 
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4 SERVO 07.2006 


06 Mind/Iron 

07 Bio-Feedback 

24 Events Calendar 

25 Robotics 

26 New Products 

35 Robo-Links 



76 Menagerie 

62 Advertiser's 


VOL. 4 NO. 7 


08 RobyteS byJeffEckert 
Stimulating Robot Tidbits 

10 GeerHead by David Geer 

The Crusher Military 
Robot Prototype! 

14 Ask Mr. RobotO by Pete Miles 

Your Problems Solved Here 

18 Twin Tweaks 

by Bryce and Evan Woolley 
Super Robonova Returns 

Rubberbands and 

Bailing Wire by Jack Buffington 
How to Record and Play Back 
Any Sound 

60 Programmable Logic 

by Gerard Fonte 
Xilinx vs. CPLD 

64 Robotic Trends by Dan 

Money Talks, Coolness Walks 

87 TidBOTS by Dave Prochnow ^ 

More Exciting Robot News! 

68 Robotics Resources 

by Gordon McComb 
Robotic Arms and Grippers 

72 Brain Matrix byPete Miles 

Three Servo Hexapod Robot Kits 

77 Appetizer by Jonathan Fant 

The Robots Are Here! ... 
Well, Almost 

79 Then and NOW by Tom Carroll 

Robots Who Care for People 

Coming 08.2006 

The FaceWalker 

SERVO 07.2006 5 

Wow, it was a great feeling that night 
knowing that our Robot Fest was once 
again a success and that we were done for 
another year. But even as our group of 
dedicated volunteers celebrated another 
successful Robot Fest over dinner, the 
conversation quickly turned to what we 
could do better next year. 

How quickly we forget the weeks of 
hard work and stress that go into 
planning, promoting, and running a Robot 
Fest! The one question that I am always 
asked is, Why do you keep volunteering 
each year? I usually ask myself that same 
question about four days before the event 
when I am totally stressed out! 

This was the sixth year for our Robot 
Fest. As usual, the weeks leading up to the 
event were exciting when we signed up a 
new robot team or group to attend the 
event but there were also the times when 
we received bad news that someone had to 
cancel. Then there is always the worry that 
no one will attend or that there will not be 
enough robots on display for the public. 

Volunteering to run an event can be 
an emotional roller coaster ride for all 
involved. The good news is that each time 
you go through the process, it really does 
get easier. It just does not seem like it at 
the time. 

To answer the question why we keep 
volunteering each year, you need to go 
back and answer the question, "Why did 
you start down this path in the first 
place?" For me, it was because I wanted 
to see the kids in our school have a new 
opportunity for a type of learning 
experience that our public school system 
was incapable of delivering alone. 

After doing some research on the 
Web and then attending an event 
sponsored by MIT called "Mind Fest — A 
Day of Playful Invention" at the legendary 
Media Lab in Cambridge, MA, I wanted to 
see what would happen if I brought a 
similar gathering of robot techies to my 
community. I was quickly able to sell the 
idea of a Robot Technology Club to other 
parents, as well as the school 
administrators at my kids' school. I 

6 SERVO 07.2006 

proposed the format as an after-school 
activity, focused on applying the 
"engineering process" to building robots. 

Having met the "fathers" of the LEGO 
Robotics Invention System (Dr. Fred 
Martin, Dr. Mitchel Resnick, and Dr. Semor 
Papiet) at the MIT Media Lab, I quickly 
decided to purchase these innovative 
construction kits for our Technology Club. 

From that point on, I was "involved." 
It was rewarding to see how much 
enjoyment the kids got from building LEGO 
robots. I experienced a lot of personal 
satisfaction each time a fifth grader 
expressed how much fun they had building 
robots. The real test of how successful our 
Technology Club was would come at 4 pm 
each Wednesday when the workshop was 
supposed to end for the day. But, instead 
of our kids waiting for the bell to ring, we 
actually had to boot them out the door! 

Another surprising measure of our 
Club's success was when teachers 
approached me with a look of total 
amazement and told me that they had 
"never seen kids so interested in what they 
were doing" and that for some reason 
they could not figure out why I never 
seemed to have a discipline problem at 
our Club meetings. 

I guess we were doing something 
right! My feelings of satisfaction from so 
much positive feedback only made me 
want to volunteer more. The one question 
that I would always ask myself was, "How 
could I make a geeky thing like the 
Technology Club COOL for the kids?" 

The idea that we came up with was 
to organize a Robot Fest for all my 
"geeky" kids at the end of each school 
year. I reasoned that the other kids who 
participated in sports and other activities 
were constantly recognized in the local 
media and at school. I wanted to provide 
a day for my kids to "be cool" — a day, 
where they could feel important and 
receive positive feedback from their peers 
and the general public that would attend 
the Robot Fest. 

I was fortunate to be associated with 
an elementary school located in a high 

Mind/Iron Continued >- 

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Larry Lemieux 


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Dave Prochnow 
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Chris Cooper 
Jeff Eckert 
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Gary Mauler 
Jonathan Fant 

Tom Carroll 

David Geer 

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Copyright 2006 by 
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Dear SERVO: 

Great magazine guys. I am going 
to get into robotics and your magazine 
is fantastic! I have some suggestions 
regarding the reader who wondered 
how he could remove a broken tap. 

All of the 10 suggestions Mr. 
Roboto gave were very good. Maybe I 

SERVO Magazine would like to sincerely 
apologize for two errors in Eric Scott's article 
"Pneumatic System Safety" in the June issue 
on page 24. First, we inadvertently mis-spelled 
his last name as Stott. Secondly, the paren-ed 
comment " ... (just come to our house!)" 
was not written by Scott. It was an in-house 
comment that was never intended to get 
printed. Our bad ... 

could add some more. I teach adults in 
a trade school in Anjou, Quebec (in 
Montreal), sometimes in the machinist 
course but mostly the CNC course. 

Additional suggestions (to 
continue the previous list): 1 1) Buy and 
use only machine taps (not hand taps). 
These are sometimes named gun taps 
or spiral point taps. The advantage of 
these is that you do not have to keep 
backing out the tap — just keep on 
going. They don't cost much more than 
the hand taps and are much easier to 
use. (For example, at KBC Tools a 3/8- 
16 manual tap sells for $3.60 CAN and 

tech area of our state. The group of 
volunteer parents working with the Club 
would not have been successful without 
the support of the school staff. I was lucky 
to have talented, committed, and 
dependable volunteers to help each week 
at the Technology Club workshops. The 
ratio of students-to-pa rents was 5:1 ! 

I truly believe this is what it takes to be 
successful when working with large groups 
of young students. The most amazing thing 
was that everyone was learning together 
how to build LEGO Mindstorm robots. Of 
course, the years of experience that my 
volunteers had in engineering and 
computer science ensured that the kids 
would be successful and not end up 
frustrated because they could not get 
something to work. 

The really hard thing for the adults was 
to NOT build the robots for the kids. We 
made sure that they worked as a team and 
learned through their mistakes. The kids 
also learned that there were "many right 
answers" — a concept that was a little bit 
different from their normal school classes. 
The kids also learned that there is more 
than one right answer to solving problems. 

The big thing for everyone to remember 
is the importance of avoiding "volunteer 
burnout." This is the responsibility of every 
volunteer, as well as the parents of the kids 
who participate. For example, even if you as 
a parent can't get off work to attend the 
club meetings or don't have the technical 
skills to coach the kids, you still need to find 
some way to volunteer to help those who are 
devoting so much of their personal time to 
help your children. 

Most people feel discouraged and put- 
upon if everything falls on their shoulders. 
After a year or two, they become frustrated 

and stop volunteering. Unfortunately, in my six 
years of running the Robot Fest, I have seen at 
least two groups where the two lead 
volunteers developed "volunteer burnout." It 
was a disappointment because they had been 
doing such a great job and their kids were 
getting an experience of a lifetime. If they had 
received better support from other parents, I 
believe that they would have still been at it 
today. The message is "get involved." 

Volunteer leaders can also take steps 
to avoid their own "volunteer burnout." 
There are two things that you can do is to 
evade this: delegate and train. I have seen 
too many volunteers try to do everything by 
themselves, mainly because "it is easier if I 
just do it myself." It may seem that way, but 
there are probably some parents who 
would love to help if they only felt like they 
were welcome and needed. The other 
thing to remember is that as a volunteer, 
you need to constantly work on training 
your replacement so that you can move 
along with your own kids. 

The last thought that I would like to 
leave with you, is that this robot technology 
that we read about each month in SERVO 
Magazine is truly a fantastic learning tool 
for your children and those in your 
community. The one thing that I like about 
it is that the kids who participate are 
actually learning a ton of real, lifelong skills 
that will give them a leg-up over their peers. 
But they think that they are just having fun. 
(We fooled them, didn't we!?) 

They learn how to work as a team, lead, 
experiment, innovate, solve problems from 
different perspectives, communicate, and 
persist in finding the best solution. These skills 
prepare them to become great engineers and 
inventors who will fulfill the never-ending 
need for technology in our society. 

a spiral point tap sells for $4.88 CAN.) 

12) Make yourself an alignment 
block. This can be any small piece of 
scrap steel (say, 3/4" by 1" by 1/2" 
thick) in which you drill a series of holes 
that are simply slide-fit holes for all the 
taps you will be using (say #4 up to 
3/8"). As an example, you could drill a 
1/4" hole for a 1/4" tap, etc. Ideally, 
you should drill these holes on a drill 
press (verify that the head of the drill 
press is reasonably square with the 
table). Then, when you wish to tap a 
hole (after you have drilled the proper 
hole - example a #7 drill for a 1/4-20 
tap), just position your new alignment 
block over the hole to be tapped, hold 
it down with one hand, insert the tap 
in the appropriate hole, and tap away. 
The alignment block will keep the tap 
at right angles to the surface being 
tapped. This works even when tapping 
in awkward positions like vertical or 
overhead. Of course, the tap-drill has 
to be drilled square to the surface for 
this to work. I made one of these 
alignment blocks about 20 years ago 
and I still have it and use it in my 
basement workshop. 

13) Buy yourself a ratchet-action 
T-handle. I bought two sizes — a small 
and a big one for about $20 each. After 
you have used one of these, you won't 
want to go back to the old T-handle! 

14) To know the right size of drill 
for each tap, get a Tap-drill chart 
(usually free). I even typed the info that 
is contained on a tap-drill chart into my 
Zire Palm, so I always have the info at 
hand. I also compiled and entered into 
my Zire Palm charts for the sizes of 
various hardware (such as socket-head 
cap screws, etc.) and various handy 
formulas for calculating threads. 

15) There was an article in the 
Oct/Nov 2002 issue of Machinist's 
Workshop on how to make your 
own simple home-made EDM machine 
of the plunging type. When asking 
for a reprint at www.homeshop, make sure you ask 
for the update information in the Dec 

Continued on page 35 

SERVO 07.2006 7 

■ rn^ 

by Jeff Eckert 

re you an avid Internet surfer 
iwho came across something 
cool that we all need to see? Are 
you on an interesting R&D group 
and want to share what you're 
developing? Then send me an 
email! To submit related press 
releases and news items, please 

- Jeff Eckert 

Bats and Roaches 
Adapt to Each Other 

A cockroach is strangely attracted 

to a tiny robot that has been coated 

with roach pheromones. 

On a somewhat less appetizing 
level is some research conducted at 
the Universite Libre de Bruxelles, in 
Belgium ( Developed 
under the European Commission's 
Future and Emerging Technologies 
(FET) Initiative and dubbed project 
Leurre, small insect-like robots 
("insbots") were fitted with two 
motors, wheels, a rechargeable 
battery, several computer processors, 
a light-sensing camera, and an array of 
infrared proximity sensors. In an exper- 
iment, they were placed in a maze of 
curved walls wherein they proved their 
ability to navigate by avoiding the 
walls, obstacles, or each other, follow 
the walls, congregate around a lamp 
beam, and even line up. 

When placed in the same area 
with cockroaches, the robots adapted 
their behavior by mimicking the ani- 

mals' movements. And when coated 
with pheromones taken from roaches, 
the robots even fooled the insects into 
thinking they were real creatures, after 
which the roaches apparently began 
to imitate the behavior of the insbots. 
(Two side projects in the Leurre pro- 
gram also experimented with sheep 
and chickens, but we won't go there.) 
And what's the point of all this? 
According to project coordinator 
Jean-Louis Deneubourg, "We believe 
farming in Europe can only survive if it 
is associated with high technology ... A 
robot interacting with animals, even if 
it is not mobile, could be used for 
numerous tasks, such as herding or 
milking. Our project demonstrates 
that the fields of biology and IT can 
work together more closely in the 
future." Details are available at 

Robotic Equipment Supports 
Minimally Invasive Surgery 

Robotic surgical devices (e.g., 
Intuitive Surgical's da Vinci system) are 
highly useful for minimally invasive 
surgery, but they are expensive and 
complicated. However, a mechanical 
engineer at Purdue University (www. is working with doctors 

to come up with a system that will be 
less expensive (about $250,000), 
portable, and still versatile enough for 
a wide variety of operations. 

The basic idea is an extension of 
laparoscopic surgery, in which a 
surgeon uses instruments inserted 
through small openings, thus, elimi- 
nating large incisions that leave scars 
and require a long recovery time. 

Without robots, surgeons manipu- 
late the laparoscopic probes with 
handles that remain outside the body. 
Using hand-held tools can be tricky 
because it is difficult to manipulate 
the devices. For example, there is the 
"fulcrum effect" in which moving the 
handle in one direction causes a probe 
to move in the opposite direction 
inside the body. But a robotic device 
can compensate for the effect. 

During robotic surgeries, the 
surgeon sits at a console and uses 
hand controls to direct robotic 
arms that move the probes and a 
camera lets the surgeon see inside 
the body during the operation. The 
camera magnifies the 
view on a computer 
screen mounted on 
the console. The 
researchers are also 
trying to incorporate 
tactile sensors into 
the robots to enable 
surgeons to "feel" 
tissue so as to better 
diagnose medical 
conditions and tie 
them to CT scanners, 
ultrasound equipment, 
and MRI devices for 

The goal is to 
come up with a 
device that is suitable for such proce- 
dures as the treatment of prostate 
cancer, stomach surgery, and even 
operations on heart valves without 
the need for open-heart surgery. 
Apparently, the system will be 
marketed by a company called 

8 SERVO 07.2006 


Pressure Profile Systems (www., which already 
sells tactile sensitive devices. 

Cable Designed for 
Continuous Twisting 

If your latest project involves 
cables that must move and flex a great 
deal, you might want to take a look at 
Lapp USA. Introduced at this year's 
National Manufacturing Week Show, 
it is designed to provide reliable 

mechanical performance on multi- 
axis robots, welding robots, and 
manipulators; to connect rotating and 
tilting tables; and in other applications 
requiring bending and torsion 

It is manufactured using flexible 
bare copper conductors, special 
polymer insulation, nonfriction tape, 
and an overall tinned copper braid 
shield, if needed. It also features an 
oil-, abrasion-, and spark-resistant 
polyurethane elastomer jacket and 
remains flexible through a tempera- 
ture range of -40 to +80°C. To locate 
your nearest dealer, just visit 

Stepper Drivers 
Available for Hobbyists 

Recently introduced by LNS 
Technologies ( is the 

MSD-62M stepper motor driver, 
designed for robots, CNC routers, 
engraving machines, security cameras, 
and a range of other build-it-yourself 
applications. It is based on the 
Allegro/Sanken SLA7062M IC chip, 
which combines low-power CMOS 
logic with high-current, high-voltage 

The MSD-62M provides versatility 

for a range of applications. Photo 

courtesy of LNS Technologies. 

power FET outputs. 

It is capable of handling motor 
winding currents of up to 3 A per 
phase, and it operates from a single 
supply voltage of 10 to 40 VDC. The 
drive works with any unipolar (six- and 
eight-wire) motor and is adjustable 
from 500 mA to 3 A via an onboard 
pot. LNS also offers the BSD-298, 
which works with bipolar (four- and 
nine-wire) motors. 

Either one will run you $89.95 
assembled and tested. Kit versions are 
also available. Neither comes with a 
power supply, which will run you 
another $129.95. SV 

SERVO 07.2006 9 



by David Geer 

Contact the author at 

The Crusher Military 
Robot Prototype! 

"Roads? It Don't Need No Stinking Roads! 


Human Creature To 
Crusher Comparison 

If you were to list the various 
capabilities we humans possess that 
make us capable of mobility in the 
most unique of environments, it might 
go something like this: we can think 
independently; we can sense our envi- 
ronment; we can plan our course of 
movement accordingly; and we can 
respond to obstacles and varying ter- 
rain by changing course and adjusting 
our weight, balance, and footing. 

Military robots become more 
useful as they become capable of more 
of the things that we can do and, 
perhaps, even more than we can do. 
Crusher is the name of a recently creat- 
ed unmanned robot vehicle that fits 
the bill. Thanks to Professor John Bares 
of the Carnegie Mellon Robotics 

Crusher easily traveling down-hill 
through brush and vegetation. 

Institute (creators of the robot vehicle) 
and Carnegie's Director of Business 
Development Steve DiAntonio, I can tell 
you all about it. 


Crusher is a one-of-a-kind, 6.5 ton 
metal alloy unmanned robot vehicle. 
Traveling on six wheels, it looks at first 
like an over-sized RC'd military toy. But 
this aluminum, titanium, and steel- 
bellied monster packs a wallop — at up 
to 26 mph — on anything that it lands 
on (watch the videos at the links listed 
in the sidebar) or that gets in its path 
(it perceives and avoids obstacles that 
are too big for it to tangle with). 

Crusher's precision mobility is 
enabled by six separate embedded 
electric motors in each of its six wheels. 
The motors are powered by a hybrid 
power system of rechargeable batter- 

Crusher crossing a creek — 
smooth sailing all the way! 

ies, and the turbo diesel generator that 
recharges them. 

The hull (courtesy of CTC 
Technologies, Pennsylvania) is "high- 
test" (my slang for heavy-duty) 
aluminum tubing with titanium 
"nodes" with an outer skin (skid plate) 
of steel. This combination gives 
Crusher a high level of shock absorp- 
tion from heavy impacts (you've really 
got to watch the videos). 

The Irish engineered suspension 
(Timony Technology, Meath) gives 
Crusher a smooth ride despite the 
usual (or man-made for testing) off- 
road hazards of huge boulder piles, 
barriers, and gulleys. 

If the Army ever needs Crusher to 
get really mean (as opposed to simply 
producing collateral damage), it can be 
fitted with more than 8,000 lbs of 
armor and weaponry payloads, as well 
as many other practical add-ons. 

Crusher can quickly increase its 
speed, even in very difficult terrain. 

1 SERVO 07.2006 


History — Beware the 
Rise of the Acronyms! 

The roots of Crusher lie in its prede- 
cessor — Spinner — and in the 
Unmanned Ground Combat Vehicle 
(UGCV) and Perception for Off-road 
Robotics (PerceptOR) projects. The two 
DARPA-funded Army programs were 
combined into the UGCV PerceptOR 
Integration (UPI) project in May of 2004. 

The first parent program — UGCV 
- started in 2001 offering up the R&D 
offspring known as Spinner — a 
durable, unmanned, off-road vehicle 
built with high performance for diffi- 
cult, off-road terrain in mind. Like some 
motored toys you may have seen, 
Spinner was most unique in that it 
had continued mobility in an inverted 
position. You could turn it completely 
over and its wheels could still touch the 
ground and keep on trucking! 

The second parent program — 
PerceptOR — which began that same 
year, prioritized sensing and autonomy 
over mobility in order to develop 
navigation skills for difficult off- 
roading challenges like trees, ditches, 
and boulders. 

The combined UPI project, which 
produced Crusher, has been funded by 
DARPA and the US Army to the tune of 
over $35 million so far. 

Crash Course in 
Crusher Mission 

Still in research, Crusher is being 


Spinner — a prototype previous to 
Crusher — was named for its ability to run 
while inverted. Crusher is named for its 
ability to climb over boulders and other 
large obstacles. 

Spinner — the six-wheeled older 
sibling to Crusher — is the unmanned 
ground combat vehicle (UGCV) that 
resulted from a Defense Advanced 
Research Projects Agency (DARPA) 
request to pour $5.5 million in funding 
into a prototype for all terrains. 

The Carnegie Mellon National 
Robotics Engineering Center's (NREC) 
Spinner was unique in its ability to keep 
moving even if it was flipped upside down. 

Other goals for the project included 
that it be easily teleoperated and able to 
hold up in moderate crash and recovery 

Spinner was proof enough of the 
potential of this course of research to 
motivate DARPA to fund the research 
and construction of its younger sibling — 
Crusher — based in part on Spinner. 

The biggest difference between the 
two robots is that Crusher has a different 
durability-to-weight ratio. It is a much 

tested with various payloads to 
determine the types of missions for 
which it will be optimal. Potential 
mission applications include: cargo 
vehicle, recon robot, soldier rescue, 
unmanned attack vehicle (with gun 
mount), and many more. It may be 
deployed in convoys that work in tan- 
dem to accomplish military objectives. 

Feeling the Crush 

Crusher — a near seven-ton 

tougher vehicle, according to John 
Bares, Associate Research Professor in 
Carnegie Mellon's Robotics Institute and 
Director of the National Robotics 
Engineering Consortium. 

Crusher is more durable than 
Spinner, despite weighing 30-percent 
less than its predecessor. It has a tougher 
"under belly" and better suspension 
than Spinner. It has a higher torque-to- 
weight ratio on the drive and a lot of 
modular improvements, as well. 

Crusher payloads include additional 
and advanced sensors, fuel, and 
supplies, ambulatory payloads for carry- 
ing injured soldiers, and even weaponry 
and armor. 

While Spinner was designed for 
inverted operation in case of flip-flops, 
Crusher was designed to simply avoid 
being turned over. Spinner's low center 
of gravity made it difficult for it to be 
turned over, anyway. By keeping 
Spinner's width and low center of gravity 
while ditching its ability to run inverted, 
researchers were able to dump some of 
the weight, cost, and complexity of the 
Spinner model for Crusher. 

unmanned vehicle — "drives by wire" 
using GPS waypoints to determine its 
next course of movement. It will soon 
be equipped with autonomous move- 
ment via various sensor packages. 
While there will always be communica- 
tions between Crusher and a human 
operator, these will be limited to 
telling Crusher where to go — how 
it gets there is up to Crusher and its 

Developed for the military by the 
Carnegie Mellon University's Robotics 
Institute's National Robotics 

Crusher surmounts a ditch, no problem. 

Crusher drives through dusty 
atmosphere, unhindered. 

Crusher being tested at Fort Knox. 

SERVO 07.2006 11 



"We need great robotics 
engineers/' says John Bares, Associate 
Professor, Carnegie Mellon Robotics 
Institute, " ... and I say that seriously in 
the sense that, for young people 
reading this, they need to go out and 
get a good math, science, and physics 
education to do well. For other 
people, give us a call — we're looking 
for great people." 

Check out the Carnegie Mellon 
Robotics Institute and contacts at 

Engineering Center, Crusher will, for 
example, be able to drive several 
meters and sense ditches, hills, humps, 
bushes, and trees on its own and 
determine whether it can go through 
or around them. 

It will sense the terrain via 
laser sensor signals that go out, and 
by taking pictures of the terrain 
with digital cameras. The laser 
range finders send out about 75,000 
pulses per second to measure 

The cameras are digital cameras 
that take a video image, digitize it 
frame-by-frame, and analyze the 
objects in the frame via the pixels 
to determine what size and type 


Crusher is an unmanned vehicle 
and, yes, it crushes things. However, 
this is only as a by-product of its 
intended purpose. Crusher was built 
to survive and keep moving against all 
terrain related odds. With these 
capabilities, and the option to add a 
wide variety of payloads, it can be 
adapted to varying field work that is 
usually performed by operational 
personnel. This, in turn, keeps soldiers 
from being put at risk for those tasks. 

The 6.5 ton, six-wheeled jugger- 
naut prototype is stronger, more 
mobile, and soon to be more 
autonomous than other experimental 
prototypes of its size and nature. 

Field overview picture of Crusher. ■ 3D model of Crusher s predecessor, Spinner. 

of object it may be. Based on 
the analysis of those pictures, it 
provides commands to its control 
system to guide its motors for 

Additional sensors on crusher 
include speed sensors on the motors, 
sensors on the suspension system 
that measure angles, pressure sen- 
sors on the suspension to measure 
force, and inertial sensors so it 
can "feel" and respond to the 
shock. There are about 1,000 sensors 
on the vehicle. They report the state 
of every component and the engine 
has all the sensors a normal engine 

The sensors and computers 
mostly communicate via TCP/IP 
and UDP through a P2P (Point-to- 
Point) protocol. 

Computer Brains 
and Programming 

Crusher has its own computer 
brain that runs the navigation 
paths. It actually has several large 
and small computers for processing 
navigation decisions and sensor 

Most of the programming of 
Crusher is written in C++. The main 
operating system is QNX — a real-time 
system for robot control. 

Beyond the basic software used 
for the robot's actuators, steering, 
and brakes, there is software 
that processes the sensor images 
so that it can analyze them for 
size and distance to determine 
whether to go around or through 

There are two approaches to 
image processing here. Traditionally, 
you would program in all the 
intelligence about the terrain that is 
available and the robot would be 
limited to working from that to 
determine an appropriate course of 

For example, you would program 
in data that would determine 
whether Crusher is looking at a tree, 
boulder, ditch, and so on. You would 
program in information that the 
robot would use as its basis for 
determining whether the obstacle 
was sufficient to warrant a change of 

This method of programming and 
processing sensor image data requires 
that you model the outside world — 
any potential environments the robot 
might face — and that requires a lot of 

An optional approach that may be 
taken at some point is to program in 
the capacity to learn. If the robot can 
learn from its mistakes — learn which 
obstacles it should avoid next time — it 
can, to this degree, do its own 
programming of a sort and you avoid 
coding in every potential obstacle at 
the start. 

Future Plans 

There are two courses that the 
UPI, Spinner, and Crusher work could 
take. It could continue on in research, 
which could make room for another 
"design cycle" and further upgrades 
and improvements, according to 

From there it would proceed to 

1 2 SERVO 07.2006 


third party research in autonomy and 
mobility, as well as other research by 
other organizations. There is a lot 
of work that could be done to even 
further advance Crusher's off-road 

Or, the Army could at any point 
decide that Crusher is ready to 
go into production for military 

According to Bares, there is also a 
third potential path for Crusher and 
its kind. The Carnegie Mellon 
Robotics Institute involves itself in 
both military and commercial robotics 
research. It may well be that we'll 
see Crusher in some commercial 
application before we see it in 

"We're trying to get these 
systems into commercial use in 
agricultural fields and mining," says 
Bares. This would be a great 
opportunity for Carnegie Mellon to 
get feedback on how such vehicles 
operate in the field as production 

It is also possible that the individ- 
ual technologies growing in research 
and inside Crusher may be inherited by 
other projects. 

Whichever course Crusher takes, in 
the mean time, other systems will 
likely be built in parallel with Crusher 
that will become more and more 


Crusher site 



Crusher videos 



Numerous other CMU 

robotics projects 


The QNX operating system 

CMU Robotics Institute and contacts 

See Crusher in Action 

Crusher is a very large, 
aggressive (as you'll judge from 
the videos), yet quiet unmanned 
vehicle. It is very smooth as it 
moves across tough terrain. Crusher 
has been tested at the National 
Robotics Engineering Center in 
Pittsburgh, PA, most frequently at a 

site off the beaten path in Somerset 

If you are a government employ- 
ee, a contractor associated with 
Future Combat Systems (FCS), or 
other robotic programs, you are 
invited to contact UPI program 
manager Dr. Larry Jackel at Ijackel to make arrangements to 
observe UPI field trials. SV 

SERVO 07.2006 13 

esident expert on all things 

PSbotic is merely an Email away. 


Tap into the sum of all human knowladga and get your questions answered here! 
From software algorithms to material selection, Mr. Roboto strives to meet you 
where you are - and what more would you expect from a complex service droid? 


and I rvm/e 

. What does vapor bot mean? 
have seen it mentioned in 
^this magazine a couple times 
ven't been able to figure out 
what it means. 

— Tim Caufman 

fl. Ah, the nebulous Vapor Bot. I 
also hear about them all the time 
and have yet had the privilege of 
actually seeing one. Well, the Vapor 
Bot is kind of like its name — a Vapor. 
A collection of gasses that floats 
around, but is not really there. A Vapor 
Bot is actually a robot that hasn't quite 
been completed. Well, in most cases, 
its construction hasn't even started, 

and many times these robots are just 
ideas and a box of parts. 

What makes Vapor Bots different 
from other uncompleted robotic 
projects is that the creators of the 
Vapor Bot talk about their robots to 
other robot builders as if it is a built (or 
almost a completed) robot. They will 
compare specifications, capabilities, 
materials, power sources, technical and 
fabrication issues, and performance. 
They will usually brag about how well 
their robot is going to perform in the 
next competition and how it will be 
able to beat certain other robots. 
When the contest comes, the robot 
builder shows up, and the mysterious 


Pete Miles 

Vapor Bot doesn't materialize. 

Now, don't misunderstand me in 
thinking that I am being critical of 
Vapor Bots and those who build them. 
I'm not. I have about a dozen Vapor 
Bots for every robot that I actually get 
around to building. This is probably 
true for most — if not all — robot 
builders. All robots begin as a Vapor 
Bot. This is the beginning of the idea. 
There are many reasons why a robot 
doesn't get built or completed, but 
that doesn't mean that the robot isn't 
real in the builder's mind's eye. 


Part Number 

Mechanical Kangaroo 



Mechanical Ostrich 



Boxing Fighter 

Two-Legged — Remote Control 


Mechanical Rabbit 



Mechanical Tiger 



Mechanical Pis 



Mechanical Beetle 



Mechanical Racing Horse 



Mechanical Dos 



Mechanical Giraffe 



Mechanical Turtle 



Mechanical Insect 

Six-Legged — Remote Control 


Wall Hugging Mouse 

Two-Wheeled — Advanced 


Line Tracking Snail 

Two-Wheeled — Advanced 


Mechanical Blow Fish 

Two-Finned — Swimming 


Table 1. Tamiya's Robot Kits. 


own. OTi 

My 10-year-old son loves 
| everything about robots and 
k wants to learn how to build his 
you recommend anything 
that would be good for a 10-year-old? 
— Beth Porter 

fl. Well, you have several choices 
here. If your son is interested in 
building things that look like 
robots, walk around like robots, and 
are simple to build, take a look at the 
simple robotics kits that are made by 
Tamiya. These are simple plastic kits 
that are easy to assemble. There are 
two-, four-, and six-legged walkers and 
some two-wheeled robots, and most 
can be purchased for less than $20. 

These kits are made out of clear 
plastic so you can see how all of the 
internal mechanisms work. They use a 
single AA battery to run the robot's 
electric motor that drives a gearbox 

14 SERVO 07.2006 

that moves a set of linkages that 
causes the legs to move. There is 
a lot of learning potential from 
these kits in that you can study 
how they work and your son can 
make copies of them to make 
larger-sized robots. 

My first robot was a one-foot 
tall copy of a simple windup tin 
robot. Table 1 shows a list of the 
different kits that Tamiya manufac- 
tures. These kits are available at 
most of your local hobby and toy 
stores for $15 to $30 each. For 
more information about these 
kits, visit Tamiya's website at and use a key 
word search of Robot Kits. The two 
Remote Control kits would enable more 
interactions with your son and offer the 
potential for a lot of modifications to 
add more capabilities (see Figure 1). 

Now, for a more advanced robot kit 
— which I highly recommend — there is 
the LEGO Mindstorms Invention system 
( If your 
son is already playing with LEGOs, then 
the Mindstorms invention system is the 
next natural progression for him. With 
this system, you can build just about any 
type of robot your imagination can 
come up with. The LEGO Mindstorms 
system uses regular parts and has some 
special LEGO sensors, motors, and a 
microcontroller (brain) called the RCX 
brick. The RCX brick can control three 
different outputs (motors) and can read 
in three different sensor inputs. 

The RCX brick is programmed with 
a PC using a graphical-based program- 
ming language which is very intuitive 
and easy to learn. Each programming 
sequence is like a LEGO brick, and the 
program is snapped together like a 
regular LEGO structure. The CD that 
comes with the kit has a step-by-step 
guided tour that teaches how to build 
three different robots and how to 
program them. Within a few hours, 
your son will have a robot built from 
scratch — programmed and following a 
black line on the ground. 

The LEGO Mindstorms Invention 
System is so popular and effective 
as a learning tool, an international 
robotics competition called FIRST LEGO 
League ( 
was created to use them to help teach 

Figure I. Tamiya's remote control Boxing Fighter and Mechanical Insect. 

9-14 year olds about science and 
technology. There are several thousand 
school teams that compete against 
each other every year in the September 
to December time-frame. If your son's 
school doesn't have a team, then talk 
to one of the school's administrators to 
get one started. I have been judging 
these events for a few years now, and 
it is absolutely amazing what the 
kids come up with using LEGOs and 
how they uniquely solve each of the 

A point to note here — there is 
going to be a new version of the LEGO 
Mindstorms kit that will be released in 
August 2006. It is called the LEGO 
Mindstorms NXT. It has more capabili- 
ties than the original Mindstorms 
Invention System, and different types 
of sensors and motors. Two of the big 
changes are in the motors and 
programming environment. The 
motors in the NXT system can be either 
continuous rotating — like with the 
Invention System — but they have the 
ability to move to a specific position 

and hold there, much like a model 
airplane servo. It still has a graphical- 
based programming environment, but 
it is more like a wiring diagram (based 
on LabView, which is 
also very intuitive to learn and use. 

After August, you should be able 
to find both sets at major department 
stores that have the larger LEGO 
selections — such as Toys R Us — or you 
can purchase them from the Internet. I 
haven't seen pricing for the NXT yet, 
but I have heard that it is going to be 
in the same price range of the regular 
Invention System. Table 2 shows a 
simple comparison between the two 
LEGO sets. For anyone getting started 
in the world of robotics, there is no bet- 
ter way than to get started using the 
LEGO robotic systems described here. 


Is it possible to connect a 

Playstation 2 controller to my 

robot so I can drive it around? 

— Seth Carson 

Minneapolis, MN 

LEGO Mindstorms 
Invention System 2*0 

LEGO Mindstorms NXT 


RCX Brick 

NXT Brick 


Two continuous DC motors 

Three servo motors (continuous 
and position control) 


Two Touch, One Light 

One Ultrasonic, One Sound, 
One Touch, One Light 

Number of Inputs 



Number of Outputs 



Programming Interface 



Number of LEGO Pieces 



Table 2. Comparison between the LEGD Mindstorms Invention and NXT systems. 

SERVO 07.2006 15 







v m 

Figure 2. Playstation Dual Shock 2 controller 
wired to a BASIC Stamp. 

fl. Actually, this is not hard to do, 
and I am surprised that more peo- 
ple aren't already doing this. The 
Playstation 2 Controller makes an excel- 
lent robot controller since it has 14 dig- 
ital switches and four analog axes. With 
this, you can control almost any feature 
on a robot. The only hard part you are 
going to have using this controller is 

finding the right connector for 
your controller to plug into. 

For some background 
information, take a look at 
two articles published in Nuts 
& Volts Magazine by Aaron 
Dahlen — June '03 and Jon 
Williams - September '03. 
Aaron's article showed how to 
use a Playstation controller to 
control a Lynxmotion (www. five-axis 
robotic arm and Jon's article 
introduced some improvements 
in the overall timing issues 
of the controller along with 
providing a more generic code 
for using the Playstation controller. Their 
articles showed me how to get a BASIC 
Stamp and the Playstation controller to 
talk to each other (see Figure 2). 

The first thing you need to do is 
build a simple electrical interface for 
the controller. Aaron introduced the 
concept of using a transistor to invert 
the clock signal from a BASIC Stamp to 

Figure 3. Electrical schematic for wiring a Playstation controller to a BASIC Stamp 












220 ohm 


220 ohm 




470 ohm 










the Playstation controller so that the 
commands can be used to simplify 
the programming. Figure 3 shows my 
version of this circuit. This interface 
circuit can be built by removing the 
transistor and the 10K resistor and 
directly connecting the clock signal line 
from the controller directly to the 470 
ohm resistor. But if this is done, then 
a manual method will be needed to 
toggle the clock line while reading in 
each bit of data from the data line. 

It turns out that not using hardware 
to invert the clock signal has a signifi- 
cant effect on the amount of time it 
takes to read in the data from a 
Playstation controller. Using the SHIFTIN 
and SHIFTOUT commands works well 
for reading in all the data from the but- 
tons and three of the four joystick posi- 
tions. But bit 7 of data from the y-axis of 
the left joystick is always set high due to 
the way the SHIFTIN command works 
and how the controller releases the data 
line. Jon's example code solves this prob- 
lem by manually generat- 
ing the clock signal for 
the last byte of data. So a 
combination of SHIFTIN, 
SHIFTOUT, and manually 
toggling the clock line 
while reading in the data 
signals ensures reading 
in all the data from the 
controller accurately. 

The manual method 
of toggling the clock line 
while reading in each 
bit of data from the 
controller works well, but 
there is a time penalty. 
With the BASIC Stamp, it 
takes about 3.5 times 
longer to work with all 1 
bytes of data that are 
transmitted between the 
Stamp and the Playstation 
controller when using the 
manual method over a 
combination of using the 
Stamp's built-in SHIFTIN, 
SHIFTOUT commands. 

With a regular 
BASIC Stamp 2, it takes 
about 145 ms to read 
the controller using a 
pure manual method, 



Vdd (+3V to +5V) 





1 6 SERVO 07.2006 

and it takes about 40 ms 
to read in the data using 
the SHIFTIN and 

SHIFTOUT command 
approach. This is a good 
example of why using 
some additional hard- 
ware along with some 
built-in commands from a 
microcontroller can great- 
ly improve the overall 
cycle timing of a project. 

Depending on your 
robot, 40 ms may be too 
long. For example, many 
robots use model airplane 
servos as drive motors 
and joint actuators, and 
these servos require their position to be 
updated every 20 ms (unless a dedicat- 
ed servo controller is being used.) 
When there is a need for speed, I like 
to use the BASIC Stamp 2px24. With 
this Stamp, the amount of time needed 
to read the Playstation controller is only 
9 ms, which is over four times faster 
than a regular BASIC Stamp 2. 

The sample program (available on 
the Nuts & Volts website, www.nuts is a simplified version of the 
program that Jon Williams published in 
his article in September '03. The sub- 
routine named PSX_TxRx is the manual 
method for toggling the clock line 
while reading in each bit of data for a 
single byte. Table 3 maps which button 
position with the DATA results from the 
controller, along with the variable 
name from the program example. All 
of the buttons are active low. 

As mentioned earlier, the hardest 
part of using a Playstation controller is 
probably finding a plug for the 
controller since this is a non-standard 
and proprietary plug design. I found a 
six-foot extension cable made by Intec 


Playstation 2 wiring 


Aaron Dahlan's article and 
Jon Williams' article 



it 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 

Byte Cmd 









0x41 in Digital Mode, 0x73 in Analog Mode 








Left Arrow 






















Right Joystick: Left = 0, Neutral = 127, Right = 255 X-Axis 




Right Joystick: Up = 0, Neutral = 127, Down = 255 Y-Axis 




Left Joystick: Left = 0, Neutral = 127, Right - 255 X-Axis 




Left Joystick: Up = 0, Neutral = 127, Down = 255 Y-Axis 

Table 3. Button and joystick position mapping from tha Playstation controller. 

( at a local 
department store for $5. The cover is 
easily popped off by pushing a small 
screwdriver in the seam between 
the top and bottom covers. 

Figure 4 shows the internal 
wiring inside this connector. The 
existing wiring can be removed and 
replaced with your own cable. Or, the 
existing cable can be cut somewhere 
along its six-foot length, and the 
wires from the cut end of the cable 
connected to your own connector. 

The pin spacing in this connec- 
tor is 0.156 inches, and the nine 
pins are divided into groups of three 
pins separated by a divider wall. A 

set of three-pin female connectors with 
0.156 inch spacing can also be used to 
plug into the connector. ! 

Figure 4. Internal view of a 
Playstation connector. 

At the 2006 Western Canadian Robot Gamesff 
Sumovore- based f bots brought it home: 

1st in Amateur 
\nd ft 3rd in Advanced 


Still better than the rest 
Still cheaper than the i 


': Acronym meaning 

SERVO 07.2006 

Last time, we began to equip the 
Robonova-1 from Hitec with an 
exosuit so it could complete 
scaled-down versions of the Tetsujin 
challenges. The three Tetsujin 
challenges — weight lifting, cylinder 
stacking, and a walking race — 
demand strength, mobility, and dexter- 
ity. Creating a single versatile suit that 
can complete all three challenges is 
likely out of the scope of many garage 
tinkerers, so the actual Tetsujin 
competition and our scaled-down 
version of it allow different suits for 
each challenge. Last time, we began 
with an exosuit for the cylinder 
stacking challenge. 

The Story Thus Far ... 

Our cylinder stacking suit relies on 
a kind of scissor action to grip the 
cylinders (as a simple mechanism for 
manipulation) and a turntable to 
relocate the stack (for better balance 
while turning, and to avoid the dangers 
of having the person inside the suit 
hurt themselves while turning). 

All of the additional mechanisms 
are powered by servos we pirated from 
FIRST Edurobot kits lying around Robot 
Central (our garage), and they are 
conveniently wired directly into the 
board of the Robonova. While the 
actual strength augmenting ability of 

this suit remains to be seen, it still mod- 
els ideas on a small scale that could 
viably be used in the full scale Tetsujin 
competition, and perhaps beyond. 

Not a Leg to Stand On 

One of the first modifications on 
our list was to fabricate leg braces. One 
of the main ideas of the leg braces was 
to ensure that the Robonova balanced 
on the turntable. Balance would be 
achieved by having the leg braces be 
firmly attached to the Robonova as 
well as the turntable, making the entire 
exosuit a single unit. The braces would 
also discourage any unwanted motion 
on behalf of the Robonova itself. 

Later modifications could 
include some kind of way to allow 
an up and down vertical motion 
within the leg braces in case the 
Robonova needs to lower itself to 
grasp the cylinders (or raise itself to 
place them), but getting the 
Robonova to balance in the first 
place is most important. So we 
fabricated some unostentatious but 
functional leg braces out of some 
scrap aluminum in Robot Central. 

Sometimes Robot Central is 
not, in fact, completely dedicated to 

1 8 SERVO 07.2006 

Super Robonova Returns 

^ roboScript v2.5 - [C:\untttted.rsf] 

Robonova Programming. 

robots and, as a consequence of that, 
some of the pieces that we fabricated 
for the Super Robonova (namely our 
leg braces) ended up on a solar 
powered boat (don't ask). Only a 
minor setback, because we had plenty 
more scrap aluminum out of which to 
remake the parts. 

The leg braces would serve the 
balancing function both when the 
Robonova is on and off, because the 
limp deactivated bot is quite a bother 
to work with. Now with the supportive 
braces, Robonova was easier to use as 
a model for further modifications with- 
out having to turn it on or reset the 
neutral position every time we wanted 
to try something in a new position. 

Other modifications that needed 
to be made included shaping the end 
effectors. The arm extensions needed 
to succeed where the Robonova's plas- 
tic fists (and human hands, in real 
world applications) fail. Since the 
exosuit could be fashioned specifically 
for each task, the end effectors for the 
cylinder stacking challenge needed 
simply to conform to the cylinders that 
required manipulation. 

Instead of tackling the ambitious 
complexity of mechanical fingers, we 
opted to fashion some simple curved 
end effectors that would conform to 
the sides of the cylinders and hold on 
to them via friction and pressure. The 
servo-powered arms of the Robonova 
would supply the pressure, and some 
rubber lining on the arm extensions 
would provide sufficient friction. 

Going Off RoboScript 

With the mechanical aspect of the 


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hack essentially complete, we were 
ready to program the Robonova. The 
Robonova comes with two methods of 
programming: text-based RoboBASIC 
and a graphical interface called 
RoboScript. For the purposes of pro- 
gramming for the Tetsujin challenges, 
RoboScript proved to be a more 
efficient method of programming. 
Events like cylinder stacking and weight 
lifting involve relatively simple motions, 
so the simplified programming was a 
nice fit. The walking race demanded 
the complex motion of walking, but 
thankfully the Robonova came with 
demo programs that took care of this 
more difficult gait. 

RoboScript conveniently labels the 
groups of servos by their respective 
appendages — right arm, left leg, etc. 
— which makes for user-friendly 
programming. Each group contains 
adjustable dials that can be manipulat- 
ed to achieve the desired position with 
the Robonova. An adjustment of the 
dial corresponds to a proportional 
movement in the servo. 

Perhaps the best accommodation 
that RoboScript offers is that if you 
have the Robonova hooked up to the 
computer while you are programming, 
adjusting a dial in the program will 
generate the corresponding motion in 
the actual Robonova; you will see the 
movements as you program them. This 
helps to take a great deal of the guess- 

work out of programming, because 
it allows the user to base their 
commands on qualitative observations 
of the Robonova and not just a series 
of abstract numbers. 

The most significant limitation of 
RoboScript is that what was just 
described is essentially the extent of 
the program. It consists entirely of 
programming individual "moves" with 
the graphical dials. It does not have the 
capacity for subroutines or loops, let 
alone sensory input, so it is really best 
suited to simple programs that do not 
include repetitive sequences of motion. 
The essential motion of the cylinder 

SERVO 07.2006 

Twin Tweslfg ... 

Cylinder Stacking. 

stacking is indeed simple; just grab- 
bing, lifting, turning, putting down, 
and releasing. But this motion does 
need to be completed several times — 
once for each cylinder. This would be a 
prime location for a FOR loop in the 
RoboBASIC, but copy and paste should 
also do the job in RoboScript. 

Stack Attack 

With the mechanical augmenta- 
tions complete and the programming 
done, it was time to test the 
Robonova's new exosuit for the cylin- 
der stacking challenge. However, our 
efforts at testing were stymied by 
another attack of the Prince Myshkin 
syndrome mentioned in the previous 
article on the "Super Robonova" — it 
was essentially incapacitated by myste- 
rious bouts of uncontrollable motion. 

The Robonova's left leg would con- 
stantly kick forward, despite attempts 
to remedy the problem with software 
by resetting the zero point and with 
hardware by resetting the servo horn 
to start the leg at a position farther 

back. And when the Robonova was 
kept on for an extended period of time 
while trying to write programs, it 
would eventually have the type of 
mechanical seizure that earned it the 
literary moniker. So, although we did 
not have a competition deadline to 
complete the project by — like entrants 
in the Tetsujin competition do — we did 
have a deadline from our editor to 
finish this project, so we effectively ran 
out of time to execute more thorough 
troubleshooting and diagnostics on the 
ailing system. 

Even so, partial tests showed the 
Robonova able to complete parts of 
the challenge, like gripping a cylinder. 
We're quite sure clever tinkerers could 
come up with some solutions to these 
mysterious problems, and we're also 
pretty sure these problems were out of 
the ordinary. But even though the 
effectiveness of our design could not 
be tested through the challenge, the 
process and implications of this project 
can still be evaluated. So what does an 
exosuit for the Robonova tell us about 
exosuits applied on a larger scale? 

Everybody, Grab a Cylinder! 

Microcosm in a 

Even though the Robonova provid- 
ed a nice opportunity to model ideas 
for Tetsujin exosuit designs, it was still 
a very simplified model because 
many of the complexities of the full 
scale competition were eliminated by 
working with the tiny bot. 

Perhaps the most obvious simplifi- 
cation achieved with the Robonova 
was in the area of safety. If the 
powered exosuit went crazy on 
Robonova, you might have to suffer 
the tragedy of buying a new servo, but 
if a full scale suit went berserk with a 
person inside you may be seriously 
dealing with a life and death situation. 

A suit with the capability to lift in 
excess of 1,000 pounds certainly has 
the power to do some serious damage 
to a human being, especially consider- 
ing the human operator is inside the 
suit itself. This means that just a single 
joint rotating too far could have disas- 
trous consequences for the operator, 
unlike a separate mechanical unit 
that would actually have to attack the 
operator in some fashion to inflict 
comparable damage. 

Carefully choosing a power source 
is another dilemma faced by Tetsujin 
competitors that we didn't have to 
worry about with the Robonova. With 
the Robonova we were able to wire the 
servos directly into the bot itself — a 
shortcut that would be akin to power- 
ing a mechanical exosuit by somehow 
hooking it up to the operator's heart or 
brain. Now, unless the Department of 
Defense has some crazy project up its 
sleeve for a future cyborg 
army, that kind of opera- 

7tion seems out of the 
realm of practical 
application. That means 
exosuit builders must 
consider how to carry or 
access a power source, 
whether it be batteries, a 
hydraulic pump, or an air 

Any of these options 
come with a host of 
design considerations 
and difficult decisions — 

20 SERVO 07.2006 

Super Robonova Returns 

should the suit carry a generator of 
some sort (or compressor or pump) to 
make it self sustaining, or should it just 
carry reserve units of power (batteries 
or tanks)? Either option would include 
the issues of placement on the suit — 
perhaps in a backpack for walking 
suits, or maybe inside turntable assem- 
blies for cylinder stackers. Or if the task 
was quite local to a small area, there 
may be the option of utilizing an off 
board power source, like a battery, 
compressor, or pump connected by 
cords or tubes. 

These issues of safety and power 
sources imply an overarching difficulty 
with the overall size of full-scale 
exosuits. The truth is that they are 
indeed big machines, and big machines 
need high safety standards, lots of 
power, and also a lot of time and effort 
during construction. 

The Robonova's exosuit was able 
to be made out of scrap aluminum 
from the garage because of the 
assumption that none of the tasks 
would demand a much stronger 
material. The same assumption cannot 
be made for full scale Tetsujin exosuits, 
so much more attention must be paid 
to materials selection and the like. 
Basically, a full-scale exosuit is quite 
literally a big challenge. 

Finally, the human body is a far 
more complex template to build 
around than the mechanical body of 
the Robonova. A quick comparison 
gives a good idea of the increased 
complexity when building around a 
person as opposed to a bipedal servo 
walker: the Robonova has only 16 
degrees of freedom, while the human 
body can be considered to have 
degrees of freedom ranging from 
the hundreds to the hundreds of thou- 
sands. That may seem like an exces- 
sive number of degrees of freedom, 
but the human body does indeed 
have a phenomenal range of motion, 
especially when forms of motion 
such as abduction (moving away), 
adduction (moving towards), flexion 
(bending), extension (stretching), 
circumduction (turning around), and 
rotation (rotation around an axis) are 
considered for each applicable joint. 
Of course, an exosuit does not need 

to be built around every degree 
of freedom, but the range of motion 
of the operator is certainly worth 

Considerations generated by the 
degrees of freedom of the operator of 
an exosuit most notably include design 
constraints. In the interests of safety, 
efficiency, and effectiveness, the 
degrees of freedom of the human 
body unused in the exosuit should be 
constrained by the design of the exo- 
suit. For example, for the cylinder 
stacking suit we modeled on the 
Robonova, only three degrees of free- 
dom were required (one for the 
turntable, one for the scissor grip, and 
one for bending over to pick up 
cylinders). The unnecessary degrees of 
freedom were constrained by pieces 
like the arm extensions and leg braces. 
These constraints were necessary to 
ensure that only the desired motion 
was achievable by the suit. 

The importance of constraints in 
exosuit design is even more evident 
when the full-scale case is considered. 
Unconstrained degrees of freedom in 
a Tetsujin suit would likely correspond 
to joints of the human operator that 
do not have an accompanying 
mechanical joint in the exosuit. For 
instance, if the cylinder stacking suit 
modeled by the Robonova was made 
for the full scale competition, one par- 
ticular degree of freedom that would 
need to be constrained for safety 
reasons would be in the waist of 
the operator. The turntable is 
intended to do the turning, but 
if the waist of the operator was 
somehow unconstrained in the 
suit, there is the possibility that 
a dangerous load could be 
applied to the operator at 
the waist, possibly resulting in 
serious injury. 

To constrain this degree of 
freedom in the operator, they 
should be somehow strapped 
into the suit to make it so that 
the exosuit itself will be the 
only thing making the risky 
motion. Of course, the operator 
should not be constrained to 
the point that it is impossible to 
operate the suit or escape the 

suit if anything goes awry, but 
designing the suit around the body of 
the operator in such a way as to 
constrain many unnecessary degrees 
of freedom should result in better 
safety, efficiency, and effectiveness of 
the design. Effective constraint 
design, however, demands careful 
attention to the subtleties of the 
human motion and could be a 
potentially quite difficult task. 

The Tetsujin competition itself, 
though, is even a simplification of the 
challenge of building exosuits for the 
real world. Real world exosuits will 
have to function in an unpredictable 
environment full of extraneous 
variables and diverse goals, much dif- 
ferent than the controlled environment 
the competition offers. 

Commercial exosuits might be 
expected to lift uneven and irregular 
loads, unlike the balanced load of a 
weighted barbell. Real world exosuits 
might also be expected to grapple with 
a range of objects, from regular cylin- 
ders to large boxes to irregular boul- 
ders. They could even be expected to 
walk downhill or uphill instead of on 
flat terrain. This is not meant to dimin- 
ish the difficulty or grandeur of the 
Tetsujin competition, but it is the 
simple truth that designing for the real 
world will be more complex than 
designing for competition. 

This seems to beg the question, 
though — why even bother with 

SERVO 07.2006 21 


Twin Twe^irs ... 

VSSm e l\ 

P>Sg - S- r,BB 


899 Moe Drive, #21 • Akron, OH 44310 

mechanical exosuits if they are so 
complex? If you have to worry about all 
these things like safety and power 
sources and the subtlety of the human 
motion, why not just go with a forklift 
or an autonomous machine of some 

In truth, many possible applica- 
tions for exosuits could be achieved 
just as effectively and perhaps more 
efficiently with existing technologies 
like forklifts. But there are still many 
applications that would benefit from 
the unique inclusion of the human 
element achieved by powered exosuit 
technology. For example, while a 
forklift might be suited to moving 
palettes of hardware around the 
Home Depot; it would not be very 
useful for a senior citizen with limited 
mobility that just needs help getting 
to the bocci ball field, or a soldier 
that could use help carrying heavy 
equipment on the uneven terrain of a 

Exosuits could also help those 
with disabilities more effectively than 
a wheelchair can, or they could 
perhaps help firefighters carry heavy 
lifesaving equipment into the heat of a 
fire. Applications like these require 
some kind of ability augmenting 
mechanical assistance that cannot 
really be effectively offered by existing 

Cutting Edge, 
Not Bleeding Edge 

The bleeding edge generally 
refers to the point in an engineering 
design where increases in cost, even 
large increases, only result in minis- 
cule increases in performance. Some 
might argue that development of 
powered exoskeletons is engineering 
at the bleeding edge of design. It 
could be said indeed exosuits could 
have practical applications, but at 
what cost? Are exosuits really the best 

The simple answer is a flat-out 
yes; exosuits are an answer to many 
applications like the ones listed above. 
The effectiveness of many of the solu- 
tions for the above listed applications is 
contingent on qualities that exosuits 

(or at least a future form of powered 
exosuits) are likely to display. 

For example, increasing mobility 
for the elderly or impaired is some- 
thing that is already achieved with 
technology like wheelchairs. Exosuits 
have distinct advantages over this 
existing technology. Some of the limi- 
tations of wheelchairs and similar 
mobility maximizing devices include 
their difficulty with terrain, cumber- 
some size, and lack of benefits in the 
area of recovery. Exosuits, once they 
reach a higher stage of development, 
have the possibility of offering the 
ability to cope with terrain by taking 
advantage of the human walking 
motion, a less cumbersome assistive 
machine by efficiently molding to the 
human form, and even some benefits 
in the area of physical therapy by 
exercising the muscles that need 
assistance in the first place. 

Similar advantages can be listed 
for many applications for powered 
exosuits, so it is clear that exosuits 
can eventually serve very practical pur- 
poses. They may be a difficult answer 
to hard problems, but that's what 
progress is about — solving the hard 
problems to improve the quality of life. 
These applications — disaster response, 
battlefield assistance, increased 
mobility for the elderly or impaired — 
are all problems that could result in a 
significant improvement in the quality 
of life if solved. And exosuits certainly 
seem to be a logical solution, even if 
they are difficult to get right. 

And because they are such a diffi- 
cult technology to develop that is why 
events like the Tetsujin competition 
play such a vital role in development. 
Events like Tetsujin act as an intermedi- 
ate bridge between the arena of ideas 
embodied by the Super Robonova and 
ambitious real world implementation. 
This isn't engineering at the bleeding 
edge; it's innovation at the forefront of 
progress. SV 


Hitec for advice on the mysterious 
servo issues. 

22 SERVO 07.2006 


TpCc© ^paDuOsQtero ©aw® @»3@ife(?©3B 

ODO]S)gjaDD©8a C xx>©D[ffl3QO^ 

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With our popular Servo Erector Set you can easily 
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If you're in Boston this July, make a point to see the 
AAAI Robot Competition and Exhibition. These folks always 
put on some unique and challenging events. This year, the 
events include The Robot Scavenger hunt in which robots 
must search the conference hotel for a list of items that 
include people and information. The items can only be 
found at specific locations and times. During their quest, the 
robots will have to deal with all the usual things found in the 
middle of a busy technical conference, including lots of 
people walking around. To succeed, a robot has to be good 
at interacting with people and the environment. 

Human interaction is further emphasized by their next 
event, named (surprise!): Human Robot Interaction. In this 
one robots are scored on their ability to complete tasks that 
fall into several categories. The easiest examples include 
recognition of and reaction to human gestures, recognition of 
human emotion and appropriate emotional expression, and 
natural language understanding and action execution. Want 
a more challenging task? How about: shared attention, com- 
mon workspace, intent detection. This task requires the robot 
to do things such as "remembering referents from previous 
sentences and being able to disambiguate 'this' and 'that'; 
following human eye gaze to determine objects of interest in 
the environment, and using shared attention in constructing 
referents in sentences or picking topics of conversation." 

These sorts of events sound like a lot of fun to me and 
they promote the development of useful, general-purpose 
robots. I'm sure somebody out there is thinking, "if they just 
added a flame-thrower and power saw." You might prefer to 
check out the War-Bots Xtreme combat event in that case! 

Know of any robot competitions I've missed? Is your 
local school or robot group planning a contest? Send an 
email to and tell me about it. Be sure to 
include the date and location of your contest. If you have a 
website with contest info, send along the URL, as well so we 
can tell everyone else about it. 

For last-minute updates and changes, you can always 
find the most recent version of the Robot Competition FAQ 

— R. Steven Rainwater 


Botball National Tournament 

Norman, OK 

Teams compete with autonomous robots built from 

standardized kits. 

Singapore Inter-School Micromouse Competition 

Great World City, Republic of Singapore 
Annual competition for student-built micromouse 
robots. Students from secondary schools, junior 
colleges, and technical schools have been partici- 
pating in this contest for 16 years. 

AAAI Mobile Robot Competition 

Boston, MA 

This long-standing competition for autonomous 
robots typically includes the Robot Challenge, in 
which robots navigate the conference center; 
Robot Rescue, in which robots must locate injured 
humans in a disaster area; and Hors d'oeuvres 
anyone? in which robots must serve and interact 
with humans. 

K'NEX K*bot World Championships 

Las Vegas, NV 

Includes three events: Two-wheel drive K*bots 

(autonomous), Four-wheel drive K*bots 

(autonomous), and Cyber K*bot Division (R/C). 

War-Bots Xtreme 

Saskatoon, Saskatchewan, Canada 
Radio-controlled vehicles destroy each other. 

AUVS International Aerial Robotics 

US Army Soldier Battle Lab, Fort Benning, GA 
Flying robots are required to complete a fully 
autonomous ingress of 3 km to an urban area, 
locate a particular structure from among many, 
identify all of the true openings in the correct 
structure, fly in or send in a sensor that can find 
one of three targets, and relay video or still 
photographs back 3 km to the origin in under 15 
minutes. And that's just one of three scenarios! 

24 SERVO 07.2006 


AUVS International Undersea Robotics 

US Navy TRANSDEC, San Diego, CA 
Autonomous underwater robots must complete 
a course with various requirements that change 
each year. 

Elevator:2010 Climber Competition 

Mountain View, CA 

Autonomous climber robot must ascend a 60 
meter scale model of a space elevator using power 
from a 10 kW Xenon search light at the base. 


Takamtsu City, Kagawa, Japan 

Described on the website as humanoid robot combat 

presented by the Kagawa Humanoid Robot Society. 


SWARC Texas Cup 

Mike's Hobby Shop, Carrolton, TX 
Radio-controlled vehicles destroy each other Texas-style. 

Robotics Showcase 

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SERVO 07.2006 25 

New Products 




Pioneering Drinkmation 

Motoman's new RoboBar™ 
HP offers complete robotic 
bartending and beverage dispensing 
solutions. Three versions are now 
available: Robobar HP, Robobar E, 
and Robobar NA 

RoboBar HP — Faster than the most 
experienced human barkeep, able to 
produce a perfectly mixed drink every 
10-15 seconds, Motoman's new 
RoboBar™ high-production model is a 
complete, self-contained robotic bar designed 
for use in casinos and other high-volume service bar applica- 
tions where human servers deliver the drinks to customers. 

The bartender is a unique, dual-arm Motoman DA9IC 
robot with a compact NXC100 controller housed in its 
base. The two manipulator arms on this innovative robot 
each have five axes of motion, and the base also rotates 
to provide an eleventh axis of motion, allowing RoboBar to 
perform a wide range of operations quickly, accurately, 
and efficiently. 

One robot arm is equipped with a simple parallel jaw 
gripper that handles cups, glasses, and beer bottles. Up to 
eight dispensing guns are mounted on the robot's other 
arm. Each gun can dispense up to 16 different ingredients 
(128 total), including liquors, mixes, juices, and wines — in 
any combination. RoboBar is not only fast, it mixes each 
drink perfectly every time, eliminating lost revenues due to 
spillage and overpours. The robot places multiple drinks 
onto a tray that shuttles in and out of the cell. A safety 
enclosure is included. The robot is highly reliable and pro- 
gramming it is simple. The user interface is intuitive and 
graphics-based. Servers enter their drink orders using a 
touch screen interface, which also identifies each drink 
on the tray. The number of drink recipes that can be 
programmed is virtually unlimited. Various options can be 
configured to customize RoboBar HP to meet the unique 
needs of specific service bar applications. 

RoboBar E — For lower-volume applications, the RoboBar 
E (Entertainment model) is a "star pourer" that draws 
people like a magnet. This model uses the same dual-arm 
DA9IC robot equipped with simple parallel jaw grippers 
mounted on each arm that allows it to operate much like 


a human bartender — only better. RoboBar E is designed 
to use a magnetic card scanner to authorize drink service. 
After a valid card swipe, the customer uses a touch screen 
to choose a beverage. The Motoman robot 

selects a cup, and then fills it with the 
appropriate beverage(s) and ice, if 
desired. The robot holds the glass or 
cup in one gripper while it pours from a 
bottle held in its other gripper. The 
robot might also move the cup to a 
dispenser for ice, beer, wine, juices, or 
soda, as needed, before placing it on a 
drink delivery slide for customer pickup. 
RoboBar E includes the robot, 
dispensers for beer, soda and juices, 
cups, and ice. A flat-panel video screen 
provides a selectable "personality" for 
your RoboBar. Customers can choose a male 

or female personality, with matching voice. The RoboBar 

personality can also be customized. 

RoboBar NA — Operating much like the RoboBar E 
model, Motoman offers a RoboBar NA (No Alcohol) 
version designed to dispense hot coffee drinks, such as 
coffee, espressos, cappuccinos, and lattes, as well as a 
variety of soft drinks, such as sodas, juices, and other 
non-alcoholic beverages. However, since no proof of 
legal drinking age is required for non-alcoholic beverage 
purchases, RoboBar NA does not require use of a 
magnetic card scanner to authorize drink service. 

The RoboBar E and NA models are available for 
purchase, lease, or event rental. The RoboBar HP model is 
available for purchase or lease only. 

For further information, please contact: 

Motoman, Inc. 

805 Liberty Ln. 
West Carrollton, OH 45449 

Tel: 937*847*6200 




Combined Six-Axis and 
Linear Robot 


UKA Robotics Corporation — a leading global 
manufacturer of industrial robots — offers the KUKA 

26 SERVO 07.2006 

New Products 

JET robot which is a six-axis robot mounted on a linear 
unit. The new robot is designed for customers with 
applications that entail long reach tasks. The six-axis 
robot is mounted either upside down or sideways 
on the linear rail, depending on the application and is 
available in four configurations with different reaches 
and working ranges. 

"Customers with applications where long distances 
need to be traversed will find the KUKA JET robot ideal," 
said Kevin Kozuszek, director of marketing for KUKA 
Robotics. "The robot combines the speed of a linear axis 
and the flexibility of a six-axis robot making it ideal for 
handling tasks in multiple industries including injection 
molding, die casting, machine tool manufacturing, and 

The KUKA JET robot's enhanced maneuverability 
allows machines to be tended through narrow openings 
and parts precisely positioned even within the machine. 
It also allows parts to be withdrawn from the machine 
in a longitudinal direction. This makes it possible to 
serve a number of machines in a row, resulting in opti- 
mal material flow. Up to two robots can be controlled 
on one linear axis. Additionally, the installation can be 
configured to allow several machines to be tended 
by one combination. Payloads range from 30 to 60 

The company's five- and six-axis robots range 
from 3 kg to 570 kg payloads, and 635 mm to 3,700 
mm reach, all controlled from a common PC based 
controller platform. KUKA robots are utilized in a 
diverse range of industries including the appliance, 
automotive, aerospace, consumer goods, logistics, 
food, pharmaceutical, medical, foundry, and 
plastics industries and in multiple applications including 
material handling, machine loading, assembly, 
packaging, palletizing, welding, bending, joining, and 
surface finishing. 

For further information, please contact: 


22500 Key Dr. 
4.1 ^ — Clinton Township, Ml 48036 

oootics v-orp* Td: 586 . 569 . 2082 Fax . 866 . 329 . 5852 



Stepper Motor Controller 

Anew low-cost single axis stepper motor controller/ 
driver from Techno-lsel is completely self-contained 
and comes ready to plug in for immediate use. It is 
capable of controlling and driving two or four phase 
stepper motors and features integrated I/O. This 
controller/driver is designed to perform a variety 
of automation-related, motion control, inspection, 

dispensing, and 
production appli- 

The con- 
troller — identi- 
fied as the 
Centurion — fea- 
tures as standard 
a 32K battery 
backed memory 
capable of storing 10 programs (switch selectable) and 
up to 5,000 motion commands, eight digital inputs, 
eight digital outputs, operator control panel, remote 
start and stop capability, manual jog feature, watchdog 
timer, and motion control software. The controller 
is designed to communicate with a PC via an RS232 
interface. Connections for I/O are made with plug-able 
screw terminals located on the controller's back panel 
and motor connection is made with a nine-pin D 

The Techno motion control software included 
with the controller, is a user-friendly, integrated 
programming environment. It features a program 
editor, compiler, communications program, and jog 
program with teach mode. The editor and compiler 
allow the editing and compilation of a motion control 
program using simple, English-style commands. The 
communications program allows complete control of 
and transfer of a program from the PC to the controller. 
The jog program allows manual positioning of the 
motor from the PC's keyboard. It also has a teach mode 
which will automatically generate a program. Once a 
program is loaded into the controller's memory, it may 
be controlled either from the PC or from the controller's 
front panel. The Centurion controller may also be 
completely disconnected from the PC for completely 
stand-alone use. 

The Centurion controller is available with a choice 
of three different motor drivers capable of providing 
continuous currents from 1-6 A per phase. 

For further information, please contact: 


S M e i 

Linear Motion 

2101 Jericho Turnpike 
New Hyde Park, NY 11040 

Systems Tel: 800* 819*3366 Fax: 516*358*2576 

Show Us What You've Got! 

Is your product innovative, less expensive, more functional, 
or just plain cool? If you have a new product that you 
would like us to run in our New Products section, please 
email a short description (300-500 words) and a photo of 
your product to: 

SERVO 07.2006 27 


Featured This Month 


,« Organizing a Combat Event 

by Kevin Berry 

30 Safety Tip — Installing Holes 

by Kevin Berry 


30 Battle Beach 4 Rocks the 

South by Kevin Berry 


3 1 Upcoming — July 

33 Results — April and May 
Technical Knowledge 

32 Tips for Combat Robot 

Builders by Steve Judd 

Product Review 

33 Vantec RDFR23 Speed 
Controller by Kevin Berry 





Organizing a Combat Event — Not 
For the Faint of Heart 

• by Kevin Berry 



Ate»° n 




to* e 




R0V)0^ c 

t area 

accord^ ££**** 




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AttP € 


e^ sa ialt^o^n 


You just left your first combat 
event and you are totally 
jazzed. The people, the destruc- 
tion, the pure fun have you 
hooked. Like many new builders, 
you want to share the fun back 
home at your school, club, or 
community. Before you rush into 
holding your first event, you need 
to think about what's required, 
and avoid some of the pitfalls new 
(and experienced) organizers 
stumble into. 

First, you need to make a 
key decision, following some- 
thing known in the combat 
community as "Judd's Law." 
Per this piece of hard-won wis- 
dom, you need to decide if 
you're holding a show or an 
event. By a commonly- 
accepted definition, in a 
"Show," the fights happen 
per a rigid schedule, and if 
someone isn't ready, they 
forfeit. In fact, at many 
shows, there is no actual 
competition outside the box — 

no winners or losers. This format 
maximizes excitement and 
predictability for the spectators 
and venue, while setting aside the 
unpredictable nature of combat 
damage, and the variable time 
needed to repair broken bots. 
This allows selling tickets for 
specifically scheduled sessions. 

An "Event," on the other 
hand, revolves around the 
builders, and spectators view on a 
"catch as catch can" basis. Sets of 
brackets, while tentatively sched- 
uled, are run only when ready, 
and fights may be postponed if 
the bots aren't repaired. This isn't 
to say that Event Organizers (EOs) 
don't try to keep things moving, 
or have alternate brackets 
planned. It's just that things are a 
bit looser — schedule-wise — and 
priority rests with the builders. 

So, you've decided on your 
format, and its time to put in 
place the "Three Ps" of an EO: 
People, Promotion, and Process. 
The combat community is very 

SERVO 07.2006 

forgiving of people who try hard and 
seek advice and assistance, but very 
critical of those who ignore good 
advice, and even tougher on those 
who try to "ego" their way through 
an obvious failure. So your approach 
should be a humble heart, a steely 
will, and lots of communication. 


The "people" part of the 
equation is critical. Many, if not 
most, disastrous event failures can be 
traced to lack of dedicated bodies to 
plan, set up, run, and tear down an 
event. While builders are VERY 
willing to pitch in, they really ought 
to be spending their time honing 
bots and charging batteries, rather 
than building an arena at the last 
second, or helping construct 
brackets. Assembling a dedicated 
staff ahead of time is one key to 
ensuring success. If the staff actually 
knows what they are doing and are 
given freedom to manage their 
areas, so much the better. But even 
having a table with a sign marked 
"Registration" with an inexperienced 
volunteer, who can take money and 
weigh bots, is a step above what 
some events wind up providing. 


Promotion is a very tough 
subject. Some EOs have learned — to 
their chagrin — that just scheduling 
an event and trusting that enough 
people will show up is a quick route 
to failure. On the other hand, starry- 
eyed expectations of rowdy crowds, 
knocking down barricades in their 
rush to buy expensive tickets haven't 
typically materialized. The news 
media has been ho-hum about the 
whole sport since TV coverage died, 
although many local papers will run 
articles if there is a "human interest" 

Hard-won experience teaches 
that, with a few notable exceptions, 
it's easier to take the event to the 
crowds, rather than drawing masses 
of people to a remote venue. Insect 

events have done well at shopping 
malls, school fairs, college open 
houses, and hobby stores. Bigger 
events have drawn crowds when 
paired with other large gatherings, 
like Labor Day's Dragon*Con in 
Atlanta, Combots shows in 
California, or ROBOIympics in San 

The second part of promotion is 
getting builders to come. The Delphi 
Forums, Builders Database, and RFL 
site are common places to advertise. 
In my experience, personal contact is 
the single best way to draw builders. 
For smaller, 20-30 bot insect events, 
I usually send 150-200 emails over 
the three months prior to the event, 
plus uncounted IM chats. This 
includes known builders, and "blind" 
emails to school districts, clubs, 
charitable organizations, clubs, and 

When I organized the insect por- 
tion of Battle Beach 2 — by actual 
count — I sent over 200 
emails to builders, and 
can't even begin to esti- 
mate the number of tele- 
phone calls and IM chats. 

veterans, and get your team (and 
outsiders) to review your planning, 
you'll do well. It's amazing how 
many obvious things get forgotten 
when you're working without a plan. 

Your plan should be in place AT 
LEAST three months before the 
event. The bigger the event, the 
farther ahead you should have your 
list ready (up to six or more months 
for large gatherings). 

Communicate, communicate, 
communicate. Answer emails and 
phone calls until you're sick of them, 
then do it again. Opinions on this 
may vary, but I'd plan to spend four 
to 10 hours a week just communicat- 
ing between your team members, 
key builders, sponsors, venue 
providers, and others. Besides the 
200 emails to builders I mentioned 
above, I know I've sent and received 
well over 500 between the key three 
to five team members who are going 
to run an event. This point cannot be 



The process of organ- 
izing any event — whether 
it's a charity walk-a-thon or 
combat robot fight — is 
simple but critical. Team 
members have to know 
what their responsibilities 
are, how much authority 
they have to make deci- 
sions, and when they are 
to complete tasks. Leading 
an all-volunteer team is 
high art, requiring a 
unique set of skills. 

There are a couple of 
components to the 
"mechanical" side of event 
organization, those being: 
have a written plan and 
communicate intensely. If 
you, as a new EO, write 
down your "to-do" list, 
solicit similar lists from 

□ Venue commitment and rules 

□ Arena(s) and setup/teardown crew 

□ Tent or area for pits, power strips, extension cords, 
tables, chairs 

□ Dirty Work area and tools 

□ Safety official 

□ Announcer, PA/boom box and music 

□ Referees, judges 

□ Frequency clips 

□ Timer, tap out lights 

□ Scales, check-in volunteer 

□ Publicly stated expectations of sportsmanship, fun, 
tough but fair fights, enforcement of safety 

□ Rule set 

□ Coordination on transportation/storage for the 
arena before and after the event 

□ Access to a large pool of experienced 

□ Crowd control devices and/or traffic directors 

□ Parking, loading zones 

□ Awards, prizes, publicity 

□ Sponsors 

□ Insurance, Fire Marshall, Public Safety 

□ First Aid kit, fire extinguisher 

□ Treasurer, entry fees, payments 

□ Lighting, signs, staff tables, and chairs 

□ Board and/or computer for brackets 

□ RFL sanctioning 

□ Builders Database 

SERVO 07.2006 29 

stressed enough — nothing kills 
an event quicker than poor or non- 
existent communication! 


Finally, here's the last key to 
running an event. (I know I said 
there's only three, but consider this 
a bonus item.) Repeat EOs have to 

have the thickest skin on any 
mammal, bar none. Survival of the 
fittest matters here, too. There will 
ALWAYS be someone who could 
have done it better, thinks you're a 
jerk, or feels unfairly treated. If 
you've followed the steps above, 
though, you know you've satisfied 
the majority of the community, and 
your reputation will grow. Nothing 

beats the satisfaction of hearing 
from happy builders that they can't 
wait for your next event. 

So, if you're excited about the 
sport and want to hold your own 
event, press ahead! Just remember 
the key ideas I've explained, and get 
ready for the headaches, stress, and 
incredible satisfaction headed your 
way. SV 

Safety Tip — Installing Holes: Drill Safety for the Home Hacker 

• by Kevin Berry 

Drilling holes is one of the most 
basic shop tasks and also one of 
the most dangerous. There are 
dozens of mistakes that can be 
made while drilling, and I've done 
them all. 

Rule #1 is to wear safety glasses. 
Everybody thinks they can do "just 
this one hole" without them, but 
getting a shaving out of your eye 
soon teaches the value of wearing 
them every single time. 

Rule #2 /s to always use clamps 
to hold the material — whether using 
a handheld drill or a press. Invariably, 
either the drill binds and the materi- 
al spins, gouging soft tissue along 
the way, or else the drill punches 
through into whatever is holding it 
(often the hand of the driller). The 
motor spinning the drill is much 
stronger than the human hand, 
otherwise we'd all just hold the bits 
in our fingers! 

Rule #3 on the hit parade is to 
properly size the drill bits to the job. 
Drilling progressively larger holes is 
often safer than trying to hog out 
a giant hole all at once. Also, a 
common mistake when using small 
diameter bits is having too much 
outside the chuck, causing them to 
snap easily. Refer to Rule #1 about 
this one. Home builders are used 
to thinking about drilling as a 
mundane task, but true machinists 
will spend ten times as long setting 
up to drill a hole, as they do 
actually spinning the bit. Safety and 
precision go hand-in-hand, but the 
material doesn't! 

In the frenzy of last minute 
building, or repairing in the pits, 
it's easy to say "this one time 
won't matter." Well, there's a 
saying my shop teacher used on us 
— "there's never time to do it 
safely, but there's always time for 
first aid." Blood is your friend, as 
long as it's on the inside. Keep it 
there! SV 

Marc DeVidts, creator of the Builders Database, 

shows how to break all three rules, plus a 

couple more! Photo courtesy of Marc DeVidts. 


by Kevin Berry 


The Robot Fighting League's South East Championships 

lattle Beach 4 was 

>held on April 8th 
and 9th, at the Volusia 
County Fairgrounds in 
Deland, FL. About 60 
bots — ranging from 
1 50 gram Fairyweights to 220 pound 
Heavyweights — slugged it out in the 
two arenas. This was a builder- 
oriented event, heavy on action. 
Several classes ran round-robin 
formats, allowing more fights per 
team than a standard double elimina- 
tion tree. Especially popular with the 
spectators were appliance demolition 
exhibitions and ad hoc rumbles. 

The new venue was much 
appreciated by builders, with air- 
conditioned pits and a hard roof to 
fend off the traditional Battle Beach 
monsoon rainstorms. While the rains 
held off this year, having both pits 

and arenas in one 
building was a much- 
appreciated perk to 
builders who came 
from as far away as 
California, Oregon, 
New York, Pennsylvania, and 
Wisconsin to enjoy the action. 

Battle Beach's sponsors included 
Vantec, 80/20 Surplus, Titanium Joe, 
Microbotparts, Ul Productions, Team 
Ninja, Team Moon, Robot Magazine, 
and, of course, SERVO Magazine. 

30 SERVO 07.2006 

Middleweight Brainstorm relies^^" 
on "offensive armor" to protect ^ 
its weapon motor. Photo courtesy 
of Team Toad. 


VkJflV K fcTi i^kl lid -Loi 




Fight Results 

Fairyweights - 1st: Doodlebug, 
Team Ninja, Pusher; 2nd: Puckthud, 
Team Thorn, Thwack; 3rd: Puckpump, 
Team Thorn, Horizontal Spinner. 

Antweights — 1st: Peligo, Berserk 
Robotics, Horizontal Spinner; 
2nd: Pirhana, Team Ninja, Vertical 
Spinner; 3rd: Pop Quiz, Team Test 
Bot, Horizontal Spinner. 

Beetleweights — 1st: John Henry, 
Legendary Robotics, Wedge; 
2nd: Ron, Overvolted Robots, 
Saw/clamper; 3rd: Creepy Crawler, 
Team-X-Bots, Wedge. 

Iantisweights — 1st: Mantis 
From Hell, Team V. Wedge; 
2nd: Thwaxident, Insane Robotics, 
Thwack; 3rd: Rhino Viper, Team 
Diamond Back, Horizontal Spinner. 

Hobbyweights - 1st: Flight Risk, 
Team Shenanigans, Horizontal 
Spinner (gasoline); 2nd: KITT, Team 
Moon, Wedge; 3rd: Test Bot, Team 
Test Bot, Lifter. 

Featherweights — 1st: Totally 
Offensive, Team Mad Overlord, 
Horizontal Blade (currently ranked #1 
in RFL); 2nd: Eat Hitch and Die, Team 
Skarn, Pusher; 3rd: Poetic Justice, 
A.G. Robotics, Wedge. 

Lightweights — 1st: Ground Zero, 
Team O-Town, Full Body Spinner; 
2nd: Crocbot, Team Gator, Speed 
Bump; 3rd: Street Thug, Skarn, 

Iiddleweights— 1st: Brainstorm, 
Big Bang Robotics, Horizontal 
Spinner; 2nd: Lionheart, Team Toad, 
Wedge; 3rd: Ice Cube, Team Toad, 

Heavyweights — 1st: Eugene, 
Team Moon, Horizontal Spinner; 
2nd: Pandemic, Weapons of 
Miniature Destruction, Vertical 

Other Awards 

(By Builder, Judge, and 
Audience Vote) 

• Best Battle Beach Rookie — Ziggy, 
CM Robotics 

• Judge's Award — Pandemic, 
Weapons of Miniature Destruction 

• Best Driver 

Fuzzy Maudlin, Team 

• Sportsmanship Award — Alex 
Grant, A.G. Robotics 

Best Engineered Robot — 
Pandemic, Weapons of Miniature 

• Best-Dressed Team — Team Toad 

Best Robot — John Henry, 
Legendary Robotic 

• Most Awesome Loss — Household 
Trash, Divine Mechanics 

John Henry — a three pound Beetleweight 
nil* f"r SERVO (August and September 2005) 
was voted "Best Robot" by builders. 



(all RFL National qualifiers) 


! ar-Bots Xtreme - WBX-III, 
Saskatoon, Saskatchewan, 




2 6. 

www. war This is Canada's 
BIGGEST combat robot tournament. 
The weight divisions range from 
Ants to Heavyweights, PLUS 

Bot Hockey. 

Team Think Tank 
Pasadena, CA 
www.teamthink Included 
at this event 
are Fairy, Ant, 
and Beetle Weight 

SNF Qualifier, 


SERVO 07.2006 31 


Tips for Combat Robot Builders 

• by Steve Judd, Team Tentacle 

Getting Started 

• Read a book or two. In particular, 
I recommend Robot Builder's 
Bonanza by Gordon McComb and 
Kickin' Bot by Grant Imahara. 

• Visit some builder's websites — 
Steven Nelson's http://, Ted Zeiger and Pete 
and my own http://architeuthis- are all good starting 

• Start small. Build a 1 lb or 3 lb 
robot first. A small robot can be built 
with inexpensive, readily-available 
parts. Small radio-controlled toys 
make an excellent platform for a first 

• Don't rule out non-combat robotic 
sports like FIRST Lego League, FIRST, 
BotBall, and others. These offer 
well-organized competitions (usually 
for school-sponsored teams) where 
you can gain a wealth of robotic 

Spending Your 
Bot Money 

• You get what you pay for. There is 
a fine line between "inexpensive" 
and cheap. 

• Know what you're buying and 
know why you are buying it. Think 
before spending your money — can 
you afford to buy a replacement if 
the item you are considering does 
not work out? 

• Don't skimp on your radio or 
speed controllers — these are the 
most crucial parts of your bot. A 
good radio can be used for years, as 
can good ESCs. 

• Buy the best quality tools you can 
afford. Some quite good tools can be 
had at very reasonable prices from 
discount suppliers, but if you can 
afford better - BUY IT. 

• Industrial surplus is your friend. 
You can get a lot of quality bot 
components from industrial surplus 
dealers, manufacturers' surplus sales 
outlets, etc. Keep Point 2 in mind 
while shopping a surplus dealer. 

Designing and Building 

• Do the most complete design you 
can. CAD software is an effective 
tool if you have it or can get it. 
"Cardboard-aided Design" is a cheap 
and effective alternative — cut the 
pieces of your bot out of cardboard 
and fit them together. The more you 
know about how your bot will be 
assembled, the easier the fabrication 
will be. 

• Keep your design as simple as it 
can be. This does not mean to build 
only simple bots — it means that you 
should not add anything to a design 
that is not there to make it stronger, 
faster, or better in some definite 
way. A well-executed simple design is 
often a lot cooler than a design so 
complicated that it's hard to execute. 

• Neatness counts! You don't score 
any match points for this, but a 
clean, well-organized interior and an 
exterior with good fit and finish will 
help you in the arena, and get you 
some "style points" in the form of 
admiration by your fellow builders. 

• Design a bot that is easy to repair 
— you will often need to make repairs 
in a hurry. 

• Remember to allow for the wiring 

harness. The wiring inside a bot 
always seems to take up a LOT more 
space than you think. 

• Don't use sheet metal screws, pop 
rivets, and the like for assembly — 
use quality bolts and machine 
screws. If your bot has a frame, weld 
the frame members together. 

• Standardize on a single fastener 
size, if possible. Fewer different sizes 
means easier repairs. 

• Set screws are bad news. Rotating 
parts should be secured to shafts 
with keys or keyless bushings (i.e., 
TranTorque, Shaftloc, etc.). 

• Pins are almost as bad as 
setscrews. If your bot is dynamically 
stable in some position, you will end 
up in that position no matter how 
unlikely it seems. Design your bot so 
you can get back on your wheels 
from any orientation. 

• Any electrical connection that can 
come loose will. All electrical connec- 
tions need to be positively secured. 
Friction fits that "feel tight enough" 
are not. 

• Thread-locking products are your 
friends. If a bolt or machine screw is 
intended to be "permanent," fix it in 
place using an appropriate thread- 
locking product. 

• Design your bot so changing radio 
frequencies is as fast and easy as 
possible. You will often be called 
upon to switch to a different 
frequency at the last minute. 


• Driving: practice, practice, 
practice. The bot needs to become 

32 SERVO 07.2006 

an extension of your body. Matches 
are won and lost when a driver 
looks away from the bots for a split 

• Show up on time with your hot 
complete and ready to run. Passing 
safety on the first try should be the 
norm — not an exception. Arriving 
early and passing safety well before 
the start of combat gives you time to 
relax and socialize with the rest of 
the competitors. 

• After a fight IMMEDIATELY serv- 
ice the robot. Just because it looks 
fine on the outside does not mean 
everything is fine on the inside. The 
time to find this out is right after your 
previous fight, not just before your 

next one, or worse, in the arena. 

• Have at least two sets of batteries 
— more if possible. You may not have 
time to fully recharge batteries 
between fights. 

• Bring spares for everything. Since 
this can add a lot to the cost, 
standardize wherever possible on 
parts commonly used by other 
builders. This will make it easier to 
get an emergency replacement part 
if you run out of spares. 

• Keep your pit area clean and well 
organized. You don't want to be 
searching for a critical part or tool for 
10 minutes when you only have 20 
minutes between fights. 

• Label your tools. All major brand 
power tools look alike. 

• Be civil. The other competitors are 
your best resource at any competi- 
tion. Most will cheerfully lend you 
tools, give advice and assistance, 
and do whatever else is in their 
power to help you out if you ask 
nicely. Just remember that everyone 
is under pressure — just like you are 
— and might be busy with their own 

• Pay close attention to the event 
staff and treat them with respect. 
They are under a lot of pressure, too. 

• Be gracious whether you win or 
lose. SV 

RDFR23 Speed Controller 

• by Kevin Berry 

Vantec's series of speed controllers are battle proven, 
and loved by many top builders. They also supply to 
law enforcement, fire department, and surveillance 
applications. Their RDFR23 model supplies up to 30 amps 
continuous DC current at 30 volts. It can also handle a 70 
amp startup surge. 

There are a variety of mixing options, from straight 
"tank steer" to linear, to special exponential curves. There is 
also a special mix just for marine applications. The RDFR23 
also provides dynamic braking, which is very nice for 
combat applications, where motors are constantly slammed 
from forward to reverse and back. 

From a durability standpoint, the community generally 
agrees this unit meets their toughness criteria. At 
the Robocide event, Lighweight Chupacabra took a 
fearsome beating from top spinner "2EZ," with virtually 
every component being sliced. The RDFR23, despite a direct 
hit, dented case and with all the wires ripped loose, worked 
perfectly when 

The folks 
at Vantec are 
big supporters 
of the sport, 
donating prizes 
at many major 

The RDFR23 measures 

4.25" x 2.7" x 1.3" and 

weighs nine ounces. 


RESULTS — April and May 

Maker Faire: April 22, — World- 
class bots battled it out in this exhibition event, 
so there were no 
winners or losers. 
Fun was had by all! 


Central Illinois 

■ ■ ■ ■ 

Rdbdtics Club 

Central Illinois Bot Brawl, May 6 — A small but enthusiastic 
set of bots fought at 
the Lakeview Museum, with 
teams from Illinois, Indiana, 
and Ohio competing. 
Solarbotics provided 

sponsorship, with assistance 

from Parallax, HobbytownUSA, and Lynxmotion. Results 

are as follows: 

• RFL Qualifier, 1 lb Combat: 1st: Skeletor, P_Robotics, 
Evan Gandola; 2nd: Killer Aluminum Sandwich, Iron Fist, 
Rob Harnden II; 3rd: Evil Doorstop III, P_Robotics, Evan 

• 500 g Sumo: 1st: Orthos, dbots, Mike Dvorsky; 2nd: 
Sumo04, Black Bots, Andrew Black; 3rd: LYBOW, Black 
Bots, Andrew Black 

• LEGO Sumo: 1st: Junior, dbots, Matthew Dvorsky; 
2nd: Mighty Man, Brooksbots, Rick Brooks; 3rd: 
Net_Op_School, P_Robotics, Evan Gandola 

SERVO 07.2006 33 

• 1 kg Sumo: 1st: Extrasensory, 
Brooksbots, Rick Brooks; 2nd: 
Exhume, Brooksbots, Rick Brooks; 
3rd: BJ, dbots, Mike Dvorsky 

• 3 kg Sumo: 1st: Cheeky-san, 
dbots, Mike Dvorsky; 2nd: Excuse, 
Brooksbots, Rick Brooks; 3rd: 
Executioner, Brooksbots, Rick 

SRJC Day Under The Oaks: May 7 - 
Fifteen insect bots competed 
in a friend- 
ly, outdo- 
ors meet. 

Results are as follows: 

• Fairyweights: 1st: VD, Team 
Fatcats, Vertical Blade (this team 
is currently ranked #1 in RFL); 
2nd: Micro Drive, Team Misfit, 
Lifter; 3rd: Baby Bunny, Team 
Misfit, Wedge; 4th: Crisp, Offbeat 

• Antweights: 1st: Pushy Little 
Bugger, Tinkers Guild, Lifter; 2nd: 
The Bomb, Team Misfit, Drum; 
3rd: MC Pee Pants, Team Fatcats, 
Drum (currently ranked #1 in RFL); 

Vertical spinner VD continues to dominate the 
RFL's Fairyweight class by scoring another 
first place win. Photo from Builders Database. 

4th: Honey Bunny, 

Team Misfit, 

Winners from the "Day Under The Oaks" 

competition (L to R: Andy Sauro, Terry Slocum, 

Zachary Lytle. Front: Danielle Donaldson). 

34 SERVO 07.2006 

BiO Feedback Continued from page 7 

2002/Jan 2003 issue of the same 
magazine (it comes out once every two 
months) for some very important 
updates on safety and modifications to 
the original article (pages 3 and 35). 
Just keep it away from children. (By 
the way, I find their site a bit hard to 

16) For lubricant, try and buy 
some tapping oil. Sometimes you can 
get some for free at machine-tool 
shows and the like. Sometimes the 
places that sell tools will give you a 
small, free sample bottle. A small 
bottle can last a long time, especially 
if you only tap once in a while. For 
aluminum, I usually dilute the tapping 
oil with Varsol. In reality, any lubricant 
would be better than tapping com- 
pletely dry — if you have to and you're 
desperate, use old motor oil. 

17) Recycle! The next time you 
throw out a toothbrush, keep it to 
clean the threads of the tap. 
Sometimes you can break a tap 
because the chips are not cleared out. 

The readers may find some of the 
following formulas useful: In these 
formulas the following terms will be 

used: Nominal Diameter (ND): This is 
the outside diameter of an external 
thread (also known as the Major 
Diameter), for instance the nominal 
diameter of a 1/2" bolt is 1/2" (.500"). 

Thread Pitch: (P) the distance 
between the crests of two consecutive 
threads (the distance from the crest of 
one thread to the crest of the next 
thread), measured along the length of 
the thread. Most inch threads are 
written in the form of: 3/8-16 where 
3/8 is the nominal diameter (outside 
dia.) (.375"), followed by the pitch, 
expressed as Threads Per Inch (TPI). In 
this case of 3/8-16, there are 16 
threads per inch, therefore one inch 
divided by 16 threads results in a 
distance between two consecutive 
thread crests of 1/16 = .0625". To use 
another example, a 3/4-10 thread has 
a pitch of 10 threads per inch = 1/10 
= .100". 

Minor Diameter (MD): The diame- 
ter that is at the root (bottom) of the 

Thread Depth (TD): The distance 
from the outside of a thread to the bot- 
tom of a thread (a radius distance, use- 

ful for machining threads on a lathe). 

Pitch Diameter (PD): The diameter 
that lies equidistant between the 
Nominal Diameter and the Minor 

All the following examples will use 
the threads of 5/16-18, for which ND = 
.3125" and the Pitch (P) = 1/18 = 

Formula: Thread Depth (TD): TD = 
.6495 * P Example: .6495 * .0555 = 
.0360". Note 1: .6495 is a constant. 
Note 2: This value is a radius value and 
is useful for machining threads on a 

Formula: Pitch Diameter (PD): PD 
= ND - (.6495 * P) Example: .3125 

- (.6495 * .0555) = .2764". Note: This 
value can be found in the Machineries 
Handbook and is the value meaured by 
a thread micrometer. 

Formula for calculating the diame- 
ter of the tap drill (if you don't have a 
tap drill chart): ND - P Example: .3125 

- .0555 = .257 = drill F. 

Minor Diameter (MD): MD = ND - 
(1.0825 * P) Example: .3125 - (1 .0825 
* .0555) = .252. 

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fid ■ 


PART 4 — A Sense of Direction 

^> by Chris Cooper 

For more information on this product, 

Last month, in our quest to create the coolest and fastest 
mobile robot on the planet, we gave the E-Maxx improved 
motor control and some new capabilities. Now it can move 
at very low speeds and maintain a constant speed in almost any 
type of terrain. It can also record the distance traveled and move 
at a specified distance and velocity. 

In this article, we'll give the 
E-Maxx a sense of direction. We'll 
work through some odometry 
calculations and add a digital 
compass. Then we'll demonstrate the 
navigation method known as dead 
reckoning — calculating the current 
position based on the distance and 
direction traveled from a known 
position. Finally, we give the modified 
E-Maxx a trial run and see how well 
we can navigate around waypoints 
and return home. 

36 SERVO 07.2006 


Odometry involves using informa- 
tion about the rotation of the wheels to 
calculate distance traveled. Since the 
encoder reads the rotation of the spur 
gear, it cannot measure wheel rotation 
directly. We must calculate wheel 
rotation using the overall reduction 
information — how much the wheel axle 
turns for each turn of the motor shaft — 
from the E-Maxx gear chart in Figure 1 . 

Overall reduction is a combination 

of the spur and pinion gear ratio, the 
internal transmission ratio, and the axle 
ratio. With the encoder mounted onto 
the center shaft of the spur gear, we 
need to remove the spur and pinion 
gear ratio from the overall reduction in 
order to get the desired transmission 
ratio. Once we have that ratio and the 
diameter of the tires, we can infer how 

Photo Above: The E-Maxx RC monster 

truck makes an excellent robotics base 

Photo courtesy of Troxxos. 


far the E-Maxx travels for each count of 
the encoder. See the sidebar for the cal- 
culation details specific to our E-Maxx. 
It's important to note that the 
distance traveled is an approximation. 
It does not take into account real-world 
factors such as wheel slippage or gear 
backlash. The difference between 
calculated and actual values is small, 
but can add up over time. One way to 
compensate for the accumulated error 
is to attach additional navigation 
sensors, especially those that use an 
external reference. A digital compass is 
not subject to accumulated errors 
because it is using a fixed external 
reference — the Earth's magnetic field. 

Adding a Digital 

For thousands of years, navigators 
have used the magnetic compass to 
help find their way. The digital compass 
we use works on the same principle. 
The Earth's magnetic field is a dipole, 
with one magnetic pole near the 
geographic North Pole and the other 
near the geographic South Pole. The 
magnetic poles differ from the 
geographic poles — which are centered 
on the Earth's axis of rotation — by 
about 1 1 .5 degrees (see Figure 2). The 
magnetic field strength on the Earth 
varies with location and covers the 
range from about .1 to 1.0 Gauss. 
It is this value that we measure to 
determine the direction of the field. 
Once we know which direction is 
magnetic North, we can use that value 
to determine our current heading. 

Figure 1 . Traxxas Gear Chart showing 
overall reduction for different gearings. 

North Pole 

North Pole 

Figure 2. Earth's magnetic and 
geographic poles differ by 1 1 .5 degrees. 

A compass is an inexpensive and 
effective solution for determining 
heading, but its readings can be 
subject to interference. Ferrous metals 
like steel, nickel, and iron will distort 
magnetic fields by attracting them. 
Un-magnetized ferrous materials 
nearby produce "soft-iron" effects. 
Magnetized ferrous materials produce 
"hard-iron" effects. 

The E-Maxx itself can have these 
effects on our compass. For example, 
the operation of the motors which con- 
tain magnets can produce "hard-iron" 
interference and the NiCad batteries 
which contain nickel can produce "soft- 
iron" interference. We can compensate 
for the "constant" soft and hard 
interference coming from the E-Maxx 

Spur Gear Chart 

64 66 70 72 

12 1st 43.36 45.99 47.30 

2nd 26.92 28.56 29.37 

1st 40.03 42.45 43.66 

2nd 24.85 26.36 27.11 



1st 36.04 37.17 39.42 40.55 

2nd 22.38 23.08 24.48 25.18 

1st 33.64 34.69 36.79 37.84 

2nd 20.89 21.54 22.85 23.50 

1st 31.54 32.52 34.49 35.48 

2nd 19.58 20.19 21.42 22.03 

1st 29.68 30.61 32.46 33.39 

2nd 18.43 19.01 20.16 20.73 

1st 28.03 28.91 30.66 

2nd 17.41 17.95 19.04 

1st 26.56 27.39 29.05 

2nd 16.49 17.01 18.04 


21 1st 

22 1st 





24.03 24.78 

14.92 15.39 

22.93 23.65 
14.24 14.69 

Do not 

use with 



Overall Reduction 

through careful calibration. This calibra- 
tion will not compensate for interfer- 
ence external to the E-Maxx, but if the 
external interference is temporary, a 
compass will still be a useful addition. 


The E-Maxx gear chart gives us the 
overall reduction ratios for first and 
second gear for each combination of 
spur and pinion gear sizes. For a 12-tooth 
pinion gear and a 72-tooth spur gear, 
the chart gives the overall gear ratio as 
47.30 in first gear, which means the motor 
rotates 47.3 times for each tire rotation. 

In order to determine how many 
times the center shaft of the spur gear 
rotates, we need to factor out the gear 
ratio component contributed by the 
spur and pinion gears. Spur and pinion 
ratio is calculated using teeth which 
gives us 72:12, and can be reduced to 

6:1. Dividing the overall ratio of 47.30 
by the spur/pinion ratio of 6 gives us 
7.88 as our transmission reduction in first 
gear. The encoder disc rotates 7.88 
times for each tire rotation. 

To determine how far the E-Maxx 
moves for each tire rotation, we need 
to calculate the circumference of the 
tire. I measured a diameter of 5.75 
inches, which gives us: 

Circumference = Pi * 5.75 inches = 
18.055 inches 

Therefore, each time the encoder 

disc rotates 7.88 times, the E-Maxx 
travels 18.055 inches. For our purposes, 
the more useful value is for each 
rotation of the encoder disc, the 
wheel travels 18.055/7.88 = 2.29 inches. 
With a 100 count encoder disc, the 
E-Maxx will travel a distance of .0229 
inches per count in first gear. If you do 
the calculations for second gear, the 
distance traveled is 0.0369 inches per 
count. Determining how far you've 
traveled then becomes: 

Total distance traveled = Encoder 
count * distance per count 

SERVO 07.2006 37 








50/60 Hz 


















Signal Gnd 





Building a 
Navigation Module 

The Devantech CMPS03 digital com- 
pass is the first sensor to be added to 
our newly created navigation module. It 
is wired to the navigation module, as in 
Figure 3, and communicates with the 
new PEC-110, added to the navigation 
module over an l 2 C (Inter-Integrated 
Circuit) bus. The CMPS03 returns the 
bearing as a value between and 3599, 


Figure 4. Diagram of the newly created 
navigation module with plenty of space 
left for more sensors. 

Figure 3. Schematic 

showing wiring of 

the CMPS03 Digital 

Compass to the 

PEC-110 Port 


representing 0- 
359.9 degrees 
with degrees 
being North, 90 
degrees being 
East, 180 degrees 
being South, and 
270 degrees 

being West. 

installing the com- 
pass, I noticed 
some "soft-iron" 
interference from 
the E-Maxx itself. 
I compensated 
by following 

the Devantech 
CMPS03 calibra- 
tion process, which can be found in the 
CMPS03 manual. 

The calibration process was very 
easy. It involves setting the compass 
into a special calibration mode and 
slowly rotating the compass 360 
degrees. All I had to do was slowly 
drive the E-Maxx in circles until the 
calibration was complete. Surprisingly, I 
found no interference occurred from 
running the motors, even with the 
compass positioned at various loca- 
tions on the deck. As a result, I mount- 
ed the compass and navigation module 
directly on the deck, as opposed to 

□□□□□ □□□□□ □□□□□ □□□□□ □□□□□ 
□□□□□ □□□□□ □□□□□ □□□□□ □□□□□ 







^□□□□□□□□□□□□n ™ 


mag ixinnniMjnn nnnnnnnnnnnnnnn c 
ppacj E" ti Sdddddddddddddddt 

HnamEiDDnnnnnfflmnnnnnnnnnnnnnnn « 

□□□□ niton □□□□□ □□□□□ 


Compass • 

using a tower or mast to isolate it from 
interference (see Figure 4). 

There are only two functional 
operations: calibrate and getBearing. 
The "calibrate" method sets the compass 
into its calibration mode. The 
"getBearing" method returns the bearing 
just as the compass returns it, as an inte- 
ger between and 3599 (see Listing 1). 

Dead Reckoning 

Dead reckoning involves estimat- 
ing current position based on the 
distance and heading traveled from a 
previously known position. By combin- 
ing measurements from the encoder 
and the compass, we can follow a set of 
waypoints. To test out the dead reckon- 
ing capabilities of the E-Maxx, I set up 
two courses, as shown in Figure 5. 

The first course was an oval lap 
around two cones. From the starting 
point, the E-Maxx moves 10 feet head- 
ing due East (90 degrees), then turns 
counter-clockwise to a heading of due 
West (270 degrees) and moves 20 feet, 
turns another 180 degrees to fast due 
East again and moves 10 feet to arrive 
back at the starting point. The second 
course requires the E-Maxx to navigate 
around three cones set up in an 
equilateral triangle. 

Steering control is accomplished 
using a PID (proportional, integral, deriv- 
ative) algorithm applied to the heading. 
The PID algorithm works to force the 
heading error to zero so that the E-Maxx 
is always pointing in the desired 
direction and does not overshoot turns. 

course is divid- 
ed into a 
series of legs, 
with each leg 
consisting of a 
heading and a 
distance to 
travel on that 
Once the E- 
Maxx travels 
the distance, 

-20 ft- 


Figure 5. Simpl 

courses test 

the E-Maxx' 






38 SERVO 07.2006 

^> PEC-1 10 — 
^> Devantech Compass CMPS03 — 

the next leg is retrieved and the E-Maxx 
slowly turns until it reaches the new 
heading. When the new heading is 
reached, the E-Maxx breaks out of the 
turn and begins traveling the distance 
of the next leg. This allows me to 
simplify calculations and ignore the dis- 
tance traveled in the turn, yet still accu- 
rately traverse the course. The code in 
Listing 2 demonstrates this approach. 

After running the first course, the 
E-Maxx was off by just three inches. 
The longer distance traveled and the 
additional turns in the second course 
caused the accumulated error to 
increase to seven inches. 


Navigation is a difficult problem, 
and I've barely scratched the surface. 
But our navigation module is off to a 
good start. We have shown that dead 
reckoning using the encoder 
and the digital compass is an 
effective way to navigate over 
short distances. As distance 
traveled and number of turns 
increased, so did our positional 
error. Nonetheless, the results 
indicate just how accurate 
dead reckoning can be. 

If dead reckoning was to be 
our only method of navigation, 
we would want to be more 
precise with respect to turning 
by taking into account turning 
radius, distance traveled in the 


^> Autonomous E-Maxx: 


^> Rossum Project Papers — 
An excellent source of infor- 
mation on robot navigation: 

^> Philips KMZ51 Application 
Notes: www.semiconductors. .html 

UNIX standard function definitions */ 

#include <stdlib.h> 
#include <unistd.h> /* 
ttinclude "machine-Bus . h" 
#ifndef COMPASS_ 
#define COMPASS_ 

struct compass_t; 

typedef struct compass_t *Compass; 

// Create a new compass reference 
Compass compass_createCompass (CommBus C, 

// Calibrate the compass 

uintl6_t compass_calibrate (Compass C) ; 

// Get the bearing 

uint!6_t compass_getBearing (Compass C) ; 

// Dispose of the compass 

void compass_disposeEncodedMotor (Compass C) 

uint8_t id) ; 

uint8_t compass_messageCallback(void* object, CAN_MESSAGE *rxMessage) j 

#endif /*COMPASS_*/ 

turn, and the velocity of the E-Maxx 
through the turn. However, we have 
different navigation techniques in store. 
In the next article, we will be 
demonstrating GPS navigation. GPS nav- 
igation is an alternative, but complimen- 
tary navigation technique that is useful 
when you know the longitude and 

latitude of where you need to go. GPS 
readings are not subject to cumulative 
errors, so it's a great way to accurately 
navigate over longer distances. We'll 
tackle GPS navigation by installing a GPS 
receiver and following a trail of GPS 
breadcrumbs just like the competitors in 
the DARPA Grand Challenge. SV 


leg = 

courseIterator->getNext ( ) ; 
( Idone ScSc leg != null) { 






Check Bus status */ 
(commbus_status (bus) != 0) { 
print f( "Failed to retreive status\n" ) ; 

; commbus_readyToTransmit (bus) ) { 

// Get our current bearing 

currentBearing = compass_getBearing ( compass ) ; 

// Pass in leg heading and current bearing into 

// steering controller to turn to correct heading 

steeringcontroller_steer (steering, 1 eg- >get Heading ( ) , currentBearing) ; 

// if we are way off (more than 10 degrees) then assume we are at a turn 

// start doing a slow turn 

if (abs (currentBearing - leg->getHeading( ) ) > 100 ) { 

encodedmotor_setRate (motor, 150 ) ; 
} else if (newLeg) { 

// Start of new leg, heading close so set the distance to travel 
encodedmotor_reset Count (motor) ; 
encodedmotor_setAbsolutePosit ion (motor, 

500, countFromDistance(leg->getDistance( ) 
newLeg = 0; 

If we've traveled the distance, get the next leg 

(encodedMotor_getCount (motor) >= countFromDistance(leg->getDistance ( ) ) { 

leg = courseIterator->getNext ( ) ; 

newLeg = 1; 

} // while 

SERVO 07.2006 39 

by Simone Davalos 

Power Tool 
Drag Racing 

Sunday! Sunday! Sunday! 

Do you know what I like 
about competitions? Certainly 
camaraderie is at the top 
of the list. Innovation, skill, and cooper- 
ation fall in there somewhere too, I'm 
sure. Of course, there's also the thrill of 
two teams competing and only one 
winner. However, there are often a few 
unsung advantages that really get 
taken for granted at most events. 
People rarely consider how great it is to 
have things like shiny new auditoriums. 
Or immaculate food service. Or, you 
know, running water and electricity. 
One very rarely goes to an event with 
the fear of tetanus, ptomaine poison- 
ing, or being accidentally sprayed in 
the face with a shotgun. 

This is why we have The Power Tool 
Drag Races. 

What is Power Tool Drag Racing, 
you ask? Why, exactly what it sounds 
like, my friends. Teams compete for 
honor and glory by racing different 
classes of machines down a 75-foot 
long track, in a one-on-one no-turns- 
required speed race. Machines range 
from straight-out-of-the-box super 
stock power tools all the way to 
Unusual Design/Top Fuel mutated 
monstrosities that may or may not have 
had some part of them involved in 
something that could be loosely 
defined as a power tool at some point 
in the past (did you get all that?). 

All of this takes place amidst cheer- 

40 SERVO 07.2006 

ing crowds of sunburned, drunken, 
nerdy gearheads. The location is a real, 
working junkyard, specially tidied up 
for the event. Never fear, however, 
there are still plenty of opportunities 
for severe injury and nasty infection. 
This is why all audience members are 
made to sign a waiver before entry. 

At the Ace International Speedway 
(also known as Ace Auto and Scrap) on 
a beautiful day in San Francisco, CA 
this past May, hundreds of Power Tool 
Race enthusiasts gathered for another 
installment of what one announcer 
called "The Death March of Fun." Fifty- 
nine racers were competing in four 
classes to see who went home with the 
glory and the prize money, and who 
remained to drown their sorrows in 
beer and 3-in-1 oil. Ages ranged from 
six weeks to 85 years old, making it 
truly fun for the whole family. 

Power Tool Drag Racing has been 
an institution in San Francisco since its 
inception five or so years ago. It's been 
covered as a four-episode series on The 
Discovery Channel, and has spawned 
numerous offshoot events in places like 
Seattle, New Orleans and The United 
Kingdom. It mostly happens every year, 
except when it doesn't, as Charlie 
Gadeken, one of the co-organizers, has 
been heard to state. Everyone loves 
power tool racing for the camaraderie 
and can-do punk rock attitude of the 
competitors. They also love it for the 
family-friendly, bloodthirsty, take-no- 
prisoners competition. 

At the crack of noon, the first 
racers were up on deck as DJ Big 
Daddy played the traditional Jimi 
Hendrix rendition of the national 
anthem. Hats were barely off of heads 
and many hearts were still covered 
when the first set of racers went 
screaming down the track. Thus began 
a solid 10 hours of racing mayhem. 

As the audience entered the event, 
the Flaming Lotus Girls Admission 
Auxiliary smilingly separated race-goers 
from their money in exchange for entry 
tickets, Official Power Tool Drag Race 
t-shirts, and racing fees. When Flaming 
Lotii aren't granting you entry or racing 
power tools, they spend their time 
building large-scale fire sculptures for 
use in places like Burning Man in 
Nevada and RoboDock in Amsterdam 
(see more at www.flaminglotus. 
com). You don't have to be female to 
be a Flaming Lotus Girl, and they are 
very, very good at what they do. Which 
is consuming huge quantities of 
propane and sending jets of flame 
hundreds of feet into the air (no really 
— their stuff makes military flame 
throwers look like prayer candles.) 

The classes for the Power Tool 
Drag Races are divided up much like 
regular drag racing. Super Stock 
vehicles are often directly off the shelf 
from any hardware store. As was dis- 
covered by the New England Belt 
Sander Racing Association (from 
whom all things power tool racing 
flow), often the most effective power 

* I What is Power Tool Drag 

Racing, you ask? ... Teams 

compete for honor and glory 

by racing different classes of 

machines down a 75-foot long 

track, in a one-on-one no- 
turns-required speed race. // 




; * \ 




Mr ^^H 

beSk * 

M^k *wa 




■ •V \-*^ 

SERVO 07.2006 41 

Power Tool Drag Racing 

tool racer is a plain and unadorned 
belt sander. Sometimes super stock 
machines can be outfitted with custom 
gear, chain or tire configurations, but 
as long as the motor and the power 
supply came out of a plain old power 
tool of some sort, it's acceptable. 

The next class is the Pro- 
Superchargers. These are the same as 
the super stock, but with more than 
one motor, and don't think the contest- 
ants don't make the most of it! 

The Awful Awful Altereds class has 
the most room for gearhead artistic 
improvisation. All motor modifications 
and power source fiddling is legal, as 
long as it definitely is recognizable 
as having parts that come off a power 

The category that has caused most 
arguments among competitors is the 
Unusual Design/Top Fuel class. In years 
past, there have always been a few 
contenders that didn't quite fit the 
standards of the class in which they 
were entered. Maybe their power 
sources were incredibly unorthodox 
(fire extinguishers, gas canisters, 12- 
gauge shotguns); maybe they were 
machines that only very loosely fit the 
interpretation of "power tool" (a sling 
shot). At any rate, to avoid any more 
knock down, drag out arguments 
among officials and competitors 
(though the organizers do always like a 

halftime show), a new class was 
created specifically for this sort of 
machine. These machines tend to be 
the most dangerous, and in a world 
where no one blinks as a fire-spitting 
tricycle in the Awful Awful Altered class 
launches itself off the track and into 
the audience, some of them are dang 
scary. This is the only class where 
officials reserve the right to pull the 
machine from competition without 
warning if it seems like it will be too 
damaging to the audience and the 
organizers' insurance premiums. 

The Funny Car class is for custom 
fabricated machines that carry one or 
more rider(s) down the track, using 
one or more motors that originated in 
a hand tool. You may think this might 
limit your ability to go as fast as 
possible, but it just depends on how 
innovative you get in finding your 
hand tools. Team Inertia Labs, long- 
time PTDR competitors, has used an 
industrial slaughterhouse saw for one 
of their funny cars, nicknamed "The 
Heifer Halfer." 

The crowd remained excited and 
well lubricated as the event wore on 
throughout the day. The Official Race 
Flag Girl kept time for the announcers, 
while a digital sign related race times 
to the judges. Only a few audience 
members at the end of the track had to 
dive out of the way of a hurtling 


Super Stock 

Unusual Designs/Top Fuel 

1st — Dewalt Assault, Dash4Cash 

1st — Big Bang Barbie, Team Schneeveis 

2nd — Magdelana, Team KISS 

2nd — foxl, Team Fox 


Sex Toys 

1st — Double Barreled, Team CTP 

1st — Scratch, Thingum 

2nd — Monorail! MonoRail!, Team 

2nd — LPD, Team LPD 


Worst Engineering 

Awful, Awful Altereds 

Paul the Plumber 

1st — NeoCon Outlook, Team 


Cutest Contestant 

2nd — Monorail! MonoRail! 

Charlotte Egeria 

Monorail!, Team Impotence 

Builder Least Likely to Get Laid 

Funny Car (Ridden) 

Lowell Nelson 

1st — Thor, Inertia Labs 

2nd — Matt Dawg Express, Team 

Safety Third Victim Award 

Plumb Crazy 

Jonathon Foote 

machine or two, and the bartenders 
were up to their necks slinging beer 
and Junkyard Hot Dogs (cooked with a 
steam iron on an aluminum foil tray! 

Team Korntee's first run with the 
super stock racer Buffer the Vampire 
Slayer (a specially modified shoe-buffer 
with wheels) ended badly when his 
drive buffer couldn't get enough 
purchase on the track and spun itself 
apart. Buffer was pressed into service 
later on at the bar to keep everyone's 
combat boots bright and shiny. 

Longtime old hands at Power Tool 
Racing, father and son Lowell and 
Steven Nelson, arrived with several of 
their machines in fine form. After a few 
fraught moments and a few stunning 
races, they went home with first and 
second place in the Super Stock 
Category, an outcome that surprised 
precisely nobody. Their racers, DeWalt 
Assault and Magdelana zipped down 
the track in a hotly debated final run, 
which awarded Lowell with First Place 
and Steven with Second. What a way 
to spend a 45th wedding anniversary! 

Huh? Wedding anniversary? Yes, 
Lowell had brought his lovely wife 
to PTDR, where she spent the last 
four hours of the event sitting in the 
passenger seat of the car, waiting to 
go home. Lowell got an award for that 
one ... (see sidebar). 

The Funny Car competition was 
chock-full of innovative racing technol- 
ogy. Along with old favorites like Team 
Phoenix (The Phoenix Chainsaw 
Chopper) and Team Washburn (Drag 
Queen), there were a few notable 
newcomers. Team Saw Werks brought 
forth a stunning display of warranty- 
voiding machinery named Stihlborn. 
Stihlborn consisted of a kiddie bicycle 
with a Stihl chainsaw motor with a 
custom-built nitrous oxide and gasoline 
injection system. Good for racing and 
doing donuts in the 7-1 1 parking lot! 

One of the really innovative ride- 
ons was Team Inertia Labs, with their 
ail-pneumatically powered racer Thor. 
Thor is built with a pair of nitrogen 
tanks compressed to 2,500 psi and two 
vintage pneumatically-powered ski I- 
saws. The saws were designed to run 

42 SERVO 07.2006 

Tim the Toolman has nothin' on this crowd. A good — and reasonably 
safe — time was had by all. All photos are courtesy of Scott Beale. 

at 250 psi, which made forcing 1,000 
psi through them to race super excit- 
ing. Added to this, the brakes failed on 
the last run of the day, nearly making 
Shane (aka Bird) winner of the PTDR 
"Safety Third" Award. Sadly, he didn't 
place in the Safety Third category. 

Team Schmokin' represented for 
the Pro-superchargers with style points, 
if nothing else. Their racer, Schmokin' 
#1 consisted of four drill motors with 
saw blade wheels, mounted on the 
bottom of a working propane grill. 
Enough cup holders for two cans of 
Tecate completed the machine as it 
sped down the track, making hot dogs 
as it raced. Mmm, meat by-products. 

The Flaming Lotus Girls incinerated 
the competition with Bunny Shark 
Mini, two four inch angle grinders 
mounted on a shocking pink frame, 
shiny wire-wheels for decoration, and 
the pre-requisite flame thrower on top. 

Girl power never looked so good. 

All was not always fun and games, 
however. Doctor Jonathan Foote (a real 
PhD!) of Rotorbrain Industries (rotor was the winner of the 
annual PTDR "Safety Third" Award for 
Excellence In Not Getting Killed, when 
an Unusual Design machine ran slightly 
amok, resulting in a teensy bit of buck- 
shot to the face. Not enough to make 
Dick Cheney jealous, but enough to 
give Nosferatu the munchies. Judge 
Dave, PTDR Statistician and All Around 
Official, comments "I had just enough 
time to say 'Hey! That thing looks like 
it's powered by a 12 gauge shotgun!' 
when the thing went off." Dr. Foote 
sustained minimal damage and 
emerged from the EMT's care with 
high spirits, commenting "It's okay, 
chicks dig scars." 

All in all it was a successful event, 
with just enough catastrophe to make 

the rest of the day interesting. 
Just like NASCAR ... or not. 

Power Tool Drag Racing 
In 2006/2007 

Come on guys, this is not rocket 
science. All you need is a power tool 
and the need for speed. As Steven 
Nelson, longtime power tool racing 
champion says, "I can build a power 
tool racer in under a day. Can you?" 

Full rules for Power Tool Drag 
Racing are available on the site 
Guidelines for starting a PTDR in your 
area are on the site as well, why not 
take a crack at it yourself? 

The event in San Francisco is 
usually in May or June every year, 
however the date does tend to shift a 
bit. Plus or minus six months. Check 
the website for details. 

SERVO 07.2006 43 


and Multiple Sensors 

Part 1 : 


e derive a sense of self and of 
our environment from thousands 
of sense organs, ranging from our 
eyes and ears to the golgi tendon organs that 
monitor our muscle contractions. Similarly, 
autonomous robots employ multiple sensors 
of different types to assess their environ- 
ment and internal state. Proprioceptive 
sensors range from pressure sensors under 
the feet of hexapods and potentiometers 
attached to the joints of robot arms to the 
wheel encoders used on carpet rovers. 
Environmental sensors include the ubiquitous ultrasound and infrared rangefinders, as 
well as the more exotic humidity sensors, accelerometers, gyroscopes, and GPS receivers. 

Although it's possible to go over- 
board with the number and type of 
sensors, in practice, cost, weight, 
space on the robot chassis, and 
availability of onboard or network 
bandwidth and processing power limit 
the sensor population. Even so, thanks 
to more powerful and affordable 
sensors, multi-core microcontrollers, 
and remote PC processing, the robotics 
community is moving en masse to 
multiple sensor autonomous robot 

PHOTO ABOVE. The infrared GP2D12 and 

ultrasonic Ping))) rangefinders mounted on 

the tilt-pan head of a hexapod. 


The code listings mentioned in this 
article are available on the SERVO 
website at 

44 SERVO 07.2006 

configurations. This first article of two 
explains how multiple sensors can be 
used to enhance the performance of 
autonomous robots and introduces the 
concept of sensor fusion. 


A robot bristling with sensors 
doesn't necessarily perform any better 
than an inexpensive carpet rover 
equipped with a single IR sensor. As 
Braitenberg notes in Vehicles, even a 
robotic Cyclops, when properly 
configured, exhibits lifelike behavior 
[1]. Conversely, although it may 
look impressive, a robot with an abun- 
dance of sensors only guarantees 
expense, significant battery drain, and 
computational overhead. 

Multiple sensors, properly config- 

ured, can enhance autonomy if they 
reflect a robot's mission, physical struc- 
ture, and operating environment. Just 
as the environment selects for the fittest 
organisms in nature, the algorithms 
used to control sensors and process 
sensor data determine how well a robot 
will perform in a given environment. 


The field of robotics has been 
transformed by the availability of 
affordable, powerful, and intelligent 
sensors. Instead of working primarily 
with raw transducers, roboticists have 
angular rate gyroscopes, GPS 
receivers, accelerometers, and solid- 
state compasses at their disposal. Even 
entry-level robot kits feature compact 
IR detectors and microcontrollers. 

However, every sensor has limita- 

by Bryan Bergeron 

tions due to design and manufacture 
and from interaction with the environ- 
ment. Sensors fail and change with time 
due to thermal settling, long-term aging, 
and physical or electrical damage. 

Whether a sensor exhibits drift or 
blatant failure, the result is the same. 
The host robot is hampered in its abili- 
ty to function in the environment — 
that is, unless provision is made for 
faulty sensors. Similarly, the variables in 
the environment and within the robot 
that are indirectly quantified by sensors 
are not completely knowable. 

As such, there is always a stochas- 
tic (random) component of distance, 
position, temperature, or other 
parameter measured by a sensor. This 
stochastic nature of sensor data is 
magnified when coupled with limited 
sensor accuracy and fidelity. 


Sensors — like most other electronic 
components — are manufactured to 
certain specifications, to suit a variety of 
applications and markets. Even the best 
sensors are produced with some degree 
of variance from the ideal. A common 
means of minimizing uncertainty in data 
due to inherent sensor variability entails 
developing a meticulous model of the 
sensor characteristics relative to the 
known environmental variations. The 
goal is to characterize sensor response 
in likely environmental situations, such 
as ambient temperature, humidity, light 
level, proximity of metal, or magnetic 
fields, as well as the passage of time. 

To illustrate variability in sensor 
data caused by the environment, 
consider the popular ultrasound sonar 
sensor, typified by the Ping))) sensor 
from Parallax. Like the Devantech 
SRF-04 and several other self-contained 
ultrasonic rangefinders, the Ping))) 
sensor operates by emitting a 40 kHz 
pulse and timing the return echo [2]. 
The sensor produces a TTL-level output 
pulse that has a width corresponding 
to time required for the pulse to travel 
to the target and back again. 


Armed with cali- 
bration data, it's possi- 
ble to correct the sen- 
sor's time readings to 
suit a particular envi- 
ronment. For exam- 
ple, temperature, and, 
to a lesser extent, 
relative humidity, 
affect the accuracy of 
distance calculations 
based on data from 
the Ping))) sensor. 

Temperature and humidity should 
be considered when working with 
ultrasonic rangefinders because they 
affect the speed at which the 40 kHz 
pulse travels from the ceramic trans- 
ducer element to the object and back 
to the receiver element of the sensor. 
The nominal speed of sound in air — 
1,130 feet per second — is an approxi- 
mation for dry air at room tempera- 
ture, at sea level, and with a typical 
C0 2 concentration. A more accurate 
figure considers the temperature, pres- 
sure, humidity, and C0 2 concentration, 
in the form of the following equation: 

Vsound = (nRT/M)V2 

where n is the adiabatic constant, 
characteristics of the gasses in air 
(nominally 1.4), R is the universal gas 
constant (8.314 J/mol K), T is the 
absolute temperature in Kelvins, and 
M is the molecular weight of the gases 
in kg/mol. In other words, the speed 
of sound in air is proportional 
to the square root of the absolute 
temperature, and increases slightly 
with increasing humidity and C0 2 
concentration [3]. 

Although technically correct, 
solving the equation with reasonable 
speed and accuracy is problematic 
using integer arithmetic on a typical 
microcontroller. A more microcon- 
troller-friendly model for the velocity of 
sound in air is: 

Vsound = 331.4 + 0.6 T c m/s 



FIGURE 1. Configuration of electronic rangefinder components. 

where T c is the temperature in degrees 
Celsius. The 331.4 figure is the speed 
of sound at degrees Celsius. The 
small contributions of humidity, air 
pressure, and C0 2 content are ignored 
in this model. 

A circuit configuration that com- 
pensates for the variability in ambient 
temperature during the operation of 
an ultrasound electronic rangefinder is 
shown in Figure 1. A Sensirion SHT1 1 
temperature and humidity chip and 
Micromega uM-FPU floating point 
coprocessor — both available from 
Parallax — are used to provide real-time 
temperature compensation. 

Listing 1 is the PBASIC program of 
an electronic rangefinder based on a 
Parallax BS2p24 and Ping))) sensor. The 
components are connected as per the 
component sheets available on the 
Parallax site (, using 
the I/O assignments provided in Listing 1 . 

Following constant and variable dec- 
larations and initialization of the temper- 
ature sensor and floating point unit, the 
ambient temperature is read from the 
SHT1 1 . Temperature data is then applied 
to the velocity approximation formula 
given above, and the results are 
displayed in the PBASIC development 
environment using the DEBUG function. 
Both uncompensated and compensated 
distances are computed and displayed. 

Tests in a room held at 21 C 
revealed that the compensated figure 
at times varied from 1 to 1.5 cm from 
the uncompensated distance measure. 
More importantly, both measures 

SERVO 07.2006 45 


Ping))) Data 
4096 Samples @ 65 cm 

66 67 68 69 70 71 72 73 74 75 76 77 78 
Microseconds - 71XX 

FIGURE 2. Frequency distribution of raw Ping)))™ time data output. 

showed variability from one measure- 
ment cycle to the next when repeat- 
edly measuring the distance between 
the Ping))) sensor and a wall. Figure 2 
shows the uncompensated time data 
produced by the Ping))) over 4096 
consecutive measures. The range of 
measures — from 7 1 66 to 7 1 78 or 1 6 

microseconds — corresponds to a 
distance range of about 0.25 cm. 

According to the specifications 
from Parallax, the Ping))) is capable of 
detecting target distances from about 
3 m up to 300 cm, with a maximum 
polling spacing of 65 |jS or about 15 
kHz. The Micromega uM-FPU floating 

FIGURE 3. Frequency distribution of unfiltered GP2D12-ADC0831 output. 


RawGP2D12-ADC0831 Data 
4096 Samples @ 68 cm 


O 10- 




a> oo 









37 38 39 40 

41 42 43 44 45 46 47 48 49 50 

ACD0831 Output 

point coprocessor is used to compute 
the adjusted distance, and to illustrate 
another approach to maximizing the 
accuracy of measurements. 

Although the BASIC Stamp pro- 
vides several workarounds for integer 
math, such as the ** and */ operators, 
most other microcontrollers provide 
support for floating point arithmetic. 
There is another reason for introducing 
the uM-FPU in the hardware design, 
which will be discussed shortly. A robot 
equipped with this temperature com- 
pensation feature should perform equal- 
ly well measuring distances inside or 
outdoors, within the operating tempera- 
ture and humidity range of the Ping))). 

A halogen desk lamp and can of 
compressed air are useful in testing 
temperature compensation responsive- 
ness. A few seconds of air can drop the 
temperature of the sensing chip 10 or 
more degrees Celsius, and positioning a 
halogen desk lamp over the SHT1 1 chip 
has the opposite effect. Note that dur- 
ing testing, cooling the SHT1 1 affects 
the sensor, but not the air between the 
Ping))) and reflecting object. 

Readers interested in further 
refining the compensation by taking 
humidity into account should review 
the paper by Olson Cramer [3] and the 
code posted by Tracy Allen of EME 
systems [4]. Conversely, for those 
interested in a temperature-only sensor, 
the DS1620 Digital Thermometer is an 
inexpensive, well-documented solution. 

Target Specificity 

Another characteristic of sensors is 
illustrated by considering another com- 
monly used sensor in robotics work: 
the Sharp GP2D12 infrared rangefind- 
er. Like the Ping))), the GP2D12 emits a 
signal that bounces off of the target 
and returns to the receiving element of 
the device. However, the similarities 
end there. The GP2D12 is an analog 
device that relies on triangulation of an 
infrared beam to measure distance 
from about 10 to 80 cm. 

Furthermore, instead of returning 
the time interval digitally encoded in 
microseconds, the GP2D12 produces 
an analog voltage that is a non-linear 
function of the distance between the 
IR emitter and the target. A higher 

46 SERVO 07.2006 

and Multiple Sensors 

GP2D1 2 Sensor 
70 mm Metal Cylinder Target 

Deviation (%) 

FIGURE 4. Ping))) sensor range and bearing sensitivity 
for a 70 mm metal cylinder target. 

Ping))) Sensor 
70 mm Metal Cylinder Target 

A0 ° 


Deviation (%) 

FIGURE 5. GP2D12 sensor range and bearing sensitivity 
for a 70 mm metal cylinder target. 

output voltage corresponds to a small- 
er emitter-target separation. 

The maximum polling frequency of 
the GP2D1 2 is significantly greater than 
that of the Ping))) at 25 kHz, which cor- 
responds to a minimum measurement 
interval of about 40 |jS. The digital ver- 
sion of the Sharp sensor is free of the 
overhead of the A-to-D converter, but 
the minimum measurement interval is 
nearly double that of the analog device. 

Listing 2 shows a minimalist 
program in PBASIC to read a GP2D12 by 
polling an ADC0831 eight-bit A-to-D 
converter. The schematic of the standard 
configuration is available on the Parallax 
site, under information for the GP2D12, 
as well as volume 5 of The Nuts & Volts 
of BASIC Stamps [5]. Aside from the 
BS2p24, GP2D12, and ADC0831, the 
only other component needed is a 
potentiometer to provide a 2.5 volt 
reference for the A-to-D converter. 

As with the Ping))), the GP2D12- 
ADC0831 combination exhibits measure- 

to-measure variability. Figure 3 shows the 
frequency distribution of 4096 consecu- 
tive samples with a wall as a target at 68 
cm. The variability roughly corresponds 
to 0.5 cm at the distance, or roughly 
twice the variability of the Ping))). 
Because of this jitter, the output of the 
ADC0831 is typically filtered by averag- 
ing several consecutive measures [5]. 

Distance accuracy wasn't consid- 
ered in this example, but there are at 
least two sources of error not 
addressed by the code in Listing 2. The 
first is variability from sensor to sensor. 
As an analog device, the nonlinear 
voltage output curve varies from one 
sensor to the next. This variability may 
be insignificant for some applications, 
but critical in others, depending on the 
accuracy requirements. 

The second source of error is the 
use of an approximation of a lineariza- 
tion function, in the form of a lookup 
table, to transform the output voltage 
level to a distance measure. Although 

solving a third or fourth order 
polynomial in real time is beyond the 
capabilities of a naked STAMP, it's 
within the limits of one equipped with 
a mathematical coprocessor, such as 
the Micromega uM-FPU. Moreover, 
Micromega offers a floating point cali- 
bration program on their website that 
can be used to create a linearizing func- 
tion specific to a particular GP2D1 2 [6]. 

Given the differences in operating 
frequencies, construction, and operat- 
ing parameters, it isn't surprising that 
the Ping))) and GP2D12 sensors 
provide different results, depending on 
the target and the environment. For 
example, consider a robot world that 
consists of an expansive garage in 
which metal cylinders (empty gallon 
paint cans) and rubber balls are ran- 
domly distributed. How will the ultra- 
sound and IR range sensors perform? 

To answer this question, a Ping))) 
and GP2D12 were mounted on a micro- 
processor-controlled tilt-pan head at a 

SERVO 07.2006 47 


Ping))) Sensor 

70 mm Rubber Ball Target 

10 Tn 

\y — p— t — r— 


It /7 2m 



I I ///////////'1.5m 


III i ' /I///V/7& 

JJ/ ///////////// "■ m 



■- + 10 


^tllll /////////// 075m 



BiS^ a5m 

WH /////// 

■ -10 

^ilM// U '^ J[ " 

T = 21 C 

Deviation (%) 


Rh = 48% 

FIGURE 6. Ping))) sensor range and bearing sensitivity 
for a 70 mm rubber ball target. 

GP2D1 2 Sensor 

70 mm Rubber Ball Target 

10 -_-, ° 7n 

/ / / / / /~~7 2m 




\\\\\l/// / 7 13m 



1 1 /////om 

mil 1 1 //////////// ] m 


\mm ///vy° 

■- + 10 

mllJItfu//////// °' 75m 


^mlul/////////// °- 6m 

r o 

■yMy^^^^°- 5m 


^^^S^^mi^w 035m 


T=21 C 

Deviation (%) 


Rh = 48% 


. GP2D12 sensor range and bearing sensitivity 

for a 70 mm rubber ball target. 

height of one meter. A target — a stan- 
dard 70 mm diameter empty paint can 
— was hung at specific distances from 
the sensor by securing the target to the 
ceiling at fixed intervals by a monofila- 
ment thread. Distance measurements 
were taken from the sensors at two 
degree increments at distances of 10, 
25, 50, 75, 100, 150, 200, 250, and 
300 cm for the Ping))) and 10, 25, 35, 
50, 75, and 100 cm for the GP2D12. 

Target was centered at one meter, 
in the same horizontal plane as the sen- 
sor, and the ambient temperature and 
relative humidity were 21 C and 48%, 
respectively. The target was suspended 
at sensor height to negate the effect of 
the floor on sensor response and to 
make the results more generalizeable. 

Figures 4 and 5 show the results 
of the study. The distance data from 
the Ping))) shows the sensor consis- 
tently overestimated the sensor-target 
distance with the metal paint can, and 
the maximum range was only 200 cm, 

48 SERVO 07.2006 

and this was side-lobe pickup. 
Maximum heads-on range was 150 
cm, or 50% of the stated range of the 
sensor. The maximum bearing varied 
from nearly ±40 degrees with the 
nearest edge of the can 10 cm from 
the sensor to approximately ±10 
degrees with the target at 1 50 cm. 

The study was repeated with the 
Ping))) mounted vertically. There was 
no significant difference, other than a 
maximum range of 1 50 cm and no side 
lobes. In comparison, the GP2D12 — 
which was programmed with the aver- 
aging filter as per Parallax documenta- 
tion — had a maximum range of 100 
cm with the empty paint can target. 
Maximum bearing varied from about 
±25 degrees at 10 cm to 4 degrees at 
100 cm. There was no difference with 
the sensor mounted vertically. 

A second study was conducted 
with a 70 mm Togu-Prien rubber ball as 
a target. The results — shown in Figures 
6 and 7 — are markedly different from 

the study based on the metal can. The 
range of the Ping))) was only 75 cm, 
compared with 100 cm for the 
GP2D12. Data from the IR rangefinder 
was roughly equivalent to that from the 
previous study, with a range accuracy 
from under to over distance estimation. 
Apparently, the sonar signature 
of the rubber ball was considerably 
less than that of the paint can. In 
contrast, the infrared signature for 
both targets was similar. This is borne 
out by Figure 8, which shows the high 
reflectivity of the rubber ball under IR 
illumination. The compressibility of 
the rubber ball likely resulted in a 
smaller signature at the 40 kHz oper- 
ating frequency of the Ping))) sensor. 


The differences in response of the 
IR and US sensors, summarized graph- 
ically in Figure 9, can be used to our 
advantage through a process referred 

and Multiple Sensors 

FIGURE 8. 70 mm diameter rubber ball target under 
IR (left) and visible light (right) illumination. 

to as sensor fusion — the use of data 
from multiple sensors to decrease the 
uncertainty of measurement. Sensor 
fusion can be implemented at the 
signal, data, feature, or decision level, 
using either identical or different 
sensors. Signal-level fusion provides a 
signal in the same form as the original, 
but with, for example, greater accuracy 
and less drift. The signals from two 
ultrasonic range sensors — both in the 
form of propagation time — can be 
fused at the signal-level, for example. 

Sensor fusion at the data level 
involves manipulation of data once it 
has been normalized to the same form 
and format. For example, even though 
the data produced by the Ping))) and 
GP2D12 are markedly different, when 
converted to centimeters, the data can 
be compared and manipulated. Figure 
9 shows the overlap of bearing and 
range for the US and IR sensors, using 
computed distance data. 

In statistical terms, the GP2D12 
displays less dispersion, compared with 
the Ping))). Fusion at the feature level 
involves specific features of the data, 
such as range only. Decision fusion 
operates at an even higher level, and is 
concerned with, for example, what 
action to take, based on sensor data. 

A simple way to employ sensor 
fusion at the signal level, whether from 
sensors of the same type or of different 
types, is illustrated in Figure 10. Using 
simply the absence or presence of 
signal from two sensors that share a 
monitoring space, it's possible to glean 
more distance and bearing information 
than possible from a single sensor. 

The cone defined by the intersection 
of range and bearing coverage for each 
sensor is defined by the presence of sig- 
nals from both sensors (A&B). Similarly, 

the area cov- 
ered by one 
sensor, exclu- 
sive of the 
area covered 
by the similar- 
ly facing sen- 
sor (A NOT B 
and B NOT A) 

can be computed, as well as the total 
area covered by both sensors (A OR B). 

Using the presence or absence of 
raw sensor data from the Ping))) and 
GP2D12, a robot can locate and avoid 
both rubber balls and paint cans on the 
garage floor more accurately than with 
data from either sensor alone. However, 
differentiating balls from cans requires 
fusion at the data level, which involves 
distance measures. Assuming the sen- 
sors are arranged to provide overlapping 
coverage (as in Figure 10), the GP2D12 
will find a rubber ball in the A&B area at 
a greater range than the Ping))), but the 
response would be reversed for a paint 
can target. 

At the decision 
fusion level, how the 
sensor data are used 
to control overall robot 
behavior is dependent 
on sequencing and 
conditional use of 
data from each sensor. 
A robot can be pro- 
grammed to respond 
to data from each sen- 
sor individually, and in 
a predefined order, as 
in Figure 11. In this 
popular configuration, 
the "other sensors" 
typically include a 
bumper switch. 

Handling data 

Bearing (Degrees) 

FIGURE 9. Overlap of bearing and range coverage of the 
Ping))) and DP2D12 with a rubber ball target. 

from the GP2D12 before that of the 
Ping))) isn't significant for a slow- 
moving carpet rover. However, for a 
fast-moving robot, the choice of which 
sensor to read first can be critical. The 
option shown in Figure 1 1 is probably a 
poor choice for a garage filled with 
empty paint cans, because the range of 
the GP2D12 is considerably less than 
that of the Ping))). Furthermore, the 
cost — in terms of potential damage to 
the robot — is probably considerably 
greater for a robot-can encounter 
compared with a robot-ball collision. 

One of many possible alternative 
fusion algorithms at the decision level is 


Sensor logic possible with sensor coverage overlap. 

\ A NOT B \ 


Sensor A 



/ BNOTA / 


Sensor B 



SERVO 07.2006 49 


M B 

FIGURE 11. Decision fusion configuration in which each sensor is 
associated with the same behavior. 

shown in Figure 12. In this example, 
Ping))) data are considered first. If 
there is no distance data from the 
ultrasonic rangefinder, then control is 
returned to the main program loop. 
This configuration allows power and 
time savings, because the additional 
sensors aren't fired at every cycle. This 
savings is at the expense of a higher 
likelihood of collision with rubber balls. 
Conditional use of sensors is a 
common practice that, if used appropri- 
ately, can improve robot performance. 
For example, in Listing 1, the tempera- 

ture is measured before every distance 
measurement. Unless the ambient tem- 
perature is highly dynamic, reading the 
temperature once during the initializa- 
tion routine would be adequate. 
Additional decision configurations are 
possible, including different behaviors 
for each sensor. A battlebot might use 
a sharp weapon to deflate balls in its 
path, but choose to bludgeon the cans. 


In working with these two sen- 

FIGURE 12. Decision fusion configuration with conditional sensor handling. 


[1] Braitenberg, Valentino., Vehicles: 
Experiments in Synthetic Psychology. 
1984, Cambridge: MIT Press. 

[2] Ping)))™ Ultrasonic Rangefinder 
(#28015). Parallax, Inc., June, 2005. 

[3] Cramer, Olson., The variation of the 
specific heat ratio and the speed of 
sound in air with temperature, pressure, 
humidity, and CO2 concentration. Journal 
of the Acoustic Society of America, 1993. 
93(5) p(5): p. 2510-6. 

[4] Allen, Tracy., Temperature & Humidity 
With the Sensirion SHTlx., 2005, www. 
em esystems. com/OL2sh tlx. h tm 

[5] Williams, Jon., Measuring Up — Up to 
80 Centimeters, That Is. The Nuts & Volts 
of BASIC Stamps, Volume 5. 2004: Parallax. 

[6] uM-FPU Application Note 4 - 
Measuring Distance with the Sharp 
GP2D12 and GP2D120 Distance Sensors, 
2005. Micromega Corporation. 

www. micromegacorp. com 

sors, there are issues of relative accu- 
racy, maximum update frequency, 
cycle spacing, coverage area, environ- 
mental specificity, and failure rates. 
From the above discussion, it should 
be obvious that there is something to 
be gained from using data from both 
sensors from the signal level to the 
decision level. Fortunately, the science 
of sensor fusion is much richer than 
the limited discussion here. 

A hexapod that has to avoid 
static obstacles on a garage floor can 
get by with a few hard-coded 
heuristics. However, when millisec- 
onds count — as in a high-speed 
autonomous vehicle or missile locked 
on a target — then intuitive methods 
used here are inadequate. The effects 
of individual differences in sensors 
and seemingly minor changes in 
ambient temperature and supply 
voltage variations are magnified. 

Furthermore, it's no longer 
sufficient to know that a target is up 
ahead somewhere — its current loca- 
tion and expected trajectory over the 
next few milliseconds become critical. 
Part 2 of this series extends the con- 
cept of sensor fusion to more power- 
ful methods that function in dynamic 
targets and environments. 

50 SERVO 07.2006 

Building (H-)Bridges 

Today's robotic creations use 
various methods — which 
are based on the physics of our 
little planet — to enable the 
motion of their main body or 
subordinate appendages. The 
various parts andpieces of these 
intelligent "things mechanical" 
use hydraulics, air pressure, 
muscle wire, and even gravity to 
invoke a mechanical displace- 
ment from Point A to Point B. 

Despite the increasing use of 
the aforementioned physical meth- 
ods in robotic equipment, the major 
component involved in making 
robotic things move is still the motor. 
Take a look at the advertisements 
and columns in SERVO. The majority 
of them have some sort of motor at 
their root. And, in most cases, if a 
motor is not in the column's or 
advertisement's mix, the electronics 
that drive or control a motor are. 

Motors are the main motiva- 
tion of this column, as well. 
However, instead of delving into the 
nuances of how motors use mag- 
netic fields to create motion, I'm 
going to show you how to build 
electronic circuitry that controls the 
activation, deactivation, and direc- 
tion of the electronic movement 
within a motor's magnetic domain. 

Driving a Brushed 
DC Motor 

Small brushed DC motors are 
fascinating. Their internal complexi- 
ty is overshadowed by their ease-of- 


use. If the motor's minimum oper- 
ating voltage is low enough, con- 
necting the brushed motor's two 
power leads across a battery is all 
that is needed to get the motor's 
shaft to rotate. The fun comes in 
when you reverse the battery's 
polarity with respect to the motor's 
power leads. The motor shaft will 
then spin in the opposite direction. 

If the brushed motor has excep- 
tional bearings supporting the shaft, 
disconnecting the battery will result 
in the shaft coasting to a stop. The 
ability of a motor to provide forward 
motion, reverse motion, and to stop 
are physical properties used by every 
robotic device that employs the serv- 
ices of a traditional electromagnetic 
motor. However, to take robotic 
advantage of the work done by a 
motor, the motor's forward, reverse, 
and stop properties must be able to 
be controlled. 

The circuit I've devised in Figure 
1a is the most basic of brushed DC 
motor control designs. A positive 
voltage that is sufficient enough to 
turn on the MOSFET applied to the 
MOSFET's gate will provide a 
ground path for the motor through 
the MOSFET which, in turn, will put 

brushed ( \^ 



by Peter Best 

the motor's shaft into motion. 

The Schottky diode that 
parallels the motor is there to allow a 
conduction path for the back EMF 
that is created by the motor coil 
when the motor shaft stops 
spinning. This type of motor control 
is great if all you want to do is drive 
the brushed DC motor full tilt in a 
single direction. If rotating the motor 
shaft in a single direction is fine, but 
you don't want your robotic device 
moving at warp speed all of the 
time, you must consider controlling 
the speed of the brushed DC motor. 

With the circuit shown in Figure 
1a, speed control is easily achieved by 
simply applying a PWM (Pulse Width 
Modulation) signal to the MOSFET's 
gate. The higher the on time (logical 
high) of the PWM signal, the faster 
the motor's shaft will spin. 

What if your little robotic 
device had to use a brushed DC 
motor and controller in the Figure 
1a configuration to move one of its 
mechanical parts from Point A to 
Point B and then return to Point A? 
I'm thinking about some really 
nasty things that have to do with 
DPDT mechanical switches to 
switch the brushed DC motor's 




h-?i PA PB ±I«-H 







F l 


FIGURE 1. (A) This is Electronics 101 stuff. If you want to see the magic 
smoke, just leave the Schottky diode out of this little circuit. Also, if you 
want to experiment with this circuit, be sure to place a 100 ohm resistor 
in series with the MOSFET gate. (B) Don't try this at home! This circuit is 
bare bones and is for illustration purposes only. Although the MOSFETs 
will switch and drive the motor per the truth table, there is no protection 
for the MOSFETs in this circuit other than their internal diodes. 





















SERVO 07.2006 51 

Building (H-)Bridges — Part 1 




R5 74HC00 























2. D1-D2 = BAT54S 

3. 74HC00-74HC08 VCC = PIN 14 

4. 74HC00-74HC08 GND = PIN 7 

5. TC4467-TC4469 VDD = PINS 15,16 

6. TC4467-TC4469 GND = PINS 7,8 

7. VCC = +5VDC 

8. DRIVE VOLTAGE >= +5VDC <= +12VDC 




74HC00 ? R6 



C5 T C6 

I O 1 

C7 | C8 T 
1uF | .1urP .1ufP .1uF| 


SCHEMATIC 1. If you take it one piece at 
a time, this is a very simple circuit to 
analyze logically. Once you understand 
how a half-bridge works here, you have 
the key to understanding what happens 
when you combine half-bridges to form 
full H-Bridges. 

power terminals into reverse mode 
that we really don't want to discuss. 
So, let's add a reverse gear to our 
brushed DC motor electronically. 

In order to switch the brushed 
DC motor's power leads between 
being sourced and sinked, you need 
the circuit in Figure 1b, which adds a 
pair of P-Channel MOSFETs (PA and 
PB) to provide the sourcing of power 
to each of the brushed DC motor's 
power leads. The sinking function is 
provided by a pair of N-Channel 
MOSFETs - NA and NB - which are 
tied to each of the brushed DC 
motor's power leads, as well. 

Note that one N-Channel MOSFET 
drain and one P-Channel MOSFET 
drain are connected to each of the 
brushed DC motor's power leads. 
Power to the brushed DC motor enters 
at the P-Channel MOSFETs' source 
pins. The brushed DC motor's power 
path to ground is provided by the sink- 
ing N-Channel MOSFETs - NA and NB. 

For the sake of discussion, let's 
assume that MOSFETs PA and NA 
associate with clockwise rotation of the 
brushed DC motor shaft and PB and NB 
associate with counter-clockwise rota- 

52 SERVO 07.2006 


tion of the brushed DC motor shaft. 
With that, to spin the motor shaft in a 
clockwise direction, we must provide 
(source) power to the motor using the 
PA MOSFET. The other motor power 
lead must somehow get to ground. The 
N-Channel MOSFET - NA - provides 
for a ground path for the motor and 
performs the sinking, or grounding, 
function upon its activation. We can 
apply the same logic for counter- 
clockwise rotation of the motor shaft 
by activating MOSFETs PB and NB. I've 
assembled a motor shaft direction 
truth table with Figures 1a andlb. 

Notice in the Figure 1 truth table 
that a couple of combinations of 
activated MOSFETs result in SMOKE. 
Never do we want to activate MOSFET 
pairs PA and NB or PB and NA at the 
same time. It's pretty obvious in 
Figure 1 b that activating these pairs in 
any combination will produce a path 
from the source voltage to ground 
through the MOSFETs, which have 
very low drain-to-source resistances. 

In other words, activating the 
PA/NB and/or PB/NA MOSFET pairs will 
produce a virtual short circuit from the 
power source to ground. If your coding 
prowess is exceptional and you feel that 
you can handle switching the MOSFET 
pairs correctly using only your firmware, 

go for it. However, some simple hard- 
ware placed in front of the MOSFET 
pairs will assure that your "perfect" 
firmware won't take the basic H-Bridge 
shown in Figure 1b into SMOKE mode. 

Controlling the 

Our main objective here is to pro- 
vide a fool-proof control mechanism 
for the MOSFET pairs that make up our 
H-Bridge. Rather than depend on "per- 
fect coding," let's employ the services 
of a couple of MOSFET driver ICs that 
bring a bit more to the table than just 
being able to drive a MOSFET gate. 

The Microchip TC4467 and 
TC4469 are four-output CMOS 
buffers/MOSFET drivers that can, by 
themselves, deliver up to 1.2A of 
peak drive current. In fact, you can 
actually drive motors that require less 
than 250 mA of current directly from 
the TC4467 or TC4469 output pins. 

The difference in the TC4467 and 
TC4469, when compared to other 
MOSFET drivers, is their inclusion of 
integral logic gates to complement 
the MOSFET drivers. Each of the four 
output drivers in both the TC4467 and 
TC4469 is front-ended by a two-input 
logic gate. The TC4467's input pair 

Building (H )Bridges — Part 1 

feeds a standard NAND gate while the 
TC4469 logic gates are configured as 
AND with an inverted input. 

I've added a 74HC00 and 74HC08 
to the TC4467 and TC4469 H-Bridge 
controller mix in Schematic 1. Be 
aware that although the components 
in Schematic 1 look to be in a full 
H-Bridge configuration, they are not. 
What you actually see in Schematic 1 
is a pair of half-bridges. PA1 and NB1 
make up one of the half-bridges and 
PB1 and NA1 comprise the other half- 
bridge. Placing jumpers across JP1 will 
combine the pair of half-bridges into a 
full H-Bridge. For now, we'll forego the 
JP1 jumpers and keep the configura- 
tion in half-bridge mode as I walk us 
through the bridge control logic. 

The idea is to not allow the vertical 
pairs of MOSFETs to be activated simul- 
taneously. So, let's logically analyze the 
logic gates to see if our protection cir- 
cuitry works. PCM (P-Channel MOSFET) 
1/2, PWM (Pulse Width Modulation) 

input. Since U4A is an AND gate with 
an inverted input, the output of U4A 
will be low, turning off MOSFET NB1. 
The PB1/NA1 half-bridge circuitry is 
identical and so are the results of 
logic levels applied to the gates of PB1 
and NA1 with relation to input levels 
applied to PCM2 and NCM2. 

PCM1, in conjunction with the 
ENABLE input, is used to turn on MOS- 
FET PA1. Introducing a logically high 
level to pin 1 of U1A with no external 
input stimulus applied to U2A results 
in both of IMA's input pins presenting 
a high logic level to the 74HC08 AND 
gate, which produces a high at pin 1 
of U3A. With the ENABLE providing a 
high input level at pin 2 of U3A, the 
TC4467 NAND gate's output goes 
logically low to turn on MOSFET PA1 . 

Here's where things get interest- 
ing. NCM1 is used to turn on MOSFET 
NB1. Let's assume PA1 is on and we 
apply a logical high to the NCM1 input 
to turn on NB1 . Again, ENABLE is active 

bridge mode. Earlier, we associated PA1 
and NA1 with clockwise rotation. So, 
to initiate clockwise motor shaft opera- 
tion, we must energize PA1 and NA1. 
Applying a logical high to the PCM1 
input will turn on PA1, which will allow 
the DRIVE VOLTAGE to flow to one of 
the brushed DC motor power leads. 

NA1 is activated by issuing a logical 
high level to the NCM2 input. Once 
NA1 is on, the brushed DC motor's 
ground path is established causing the 
brushed DC motor's shaft to turn in a 
clockwise direction. To shift the brushed 
DC motor's shaft into reverse, we must 
remove the input stimulus from PCM1 
and NCM2 and apply logical high levels 
to PCM2 and NCM1. The removal of 
clockwise stimulus before applying the 
counter-clockwise logic levels is neces- 
sary because we are actually controlling 
an independent pair of half-bridges. 

If we were to jumper pins 1 to 2, 
3 to 4, and 5 to 6, applying a logical 
high to PMC1 or NCM2 would turn on 

"Today's robotic creations use various methods — which 

are based on the physics of our little planet — to enable the 

motion of their main body or subordinate appendages." 

1/2, and NCM (N-Channel MOSFET) 
1/2 are all bridge control inputs. Let's 
look at what the PA1 and NB1 MOSFET 
gates look like logically with no input 
stimulus on the PCM1, PWM1, and 
NCM1 inputs. Assume the ENABLE line 
to be active, or logically high. 

Since pin 1 of U1 A is pulled low, 
the output of AND gate U1A will be 
logically low regardless of the logic 
level applied to U1A pin 2. With the 
ENABLE line held at a logically high 
level, the inputs currently being applied 
to the TC4467 NAND driver will pro- 
duce a high level on the output of U3A, 
which turns PA1 off. With one input 
pulled high and the other pulled low, 
U2A's output pin will be logically high. 

The high level on the output of 
U2A feeds the invert input pin on the 
TC4469 MOSFET driver. Thus, pin 2 of 
TC4469 is effectively a logical low 

and is held in a logical high state. 
Taking NCM1 logically high produces a 
logical low on the output pin of the 
NAND gate U2A, which feeds a low to 
the input of AND gate U1A, which 
drives the output pin of U1A low, 
which drives the output pin of NAND 
gate U3A high and turns off PA1 . 

Meanwhile, the low level on the 
output pin of NAND gate U2A feeds 
the inverted input pin of the TC4469 
AND gate, which results in a high 
being fed to the gate of NB1 turning 
the N-Channel MOSFET on. Once 
again, the control input logic that 
works for PA1 and NB1 works identi- 
cally for PB1 and NA1. 

Okay, our MOSFET protection cir- 
cuitry works great on paper. Let's check 
out the logic again and make sure we 
can actually turn the brushed DC motor 
shaft in both directions using half- 

PA1 and NA1 and result in clockwise 
rotation of the brushed DC motor's 
shaft. Applying a logical high to the 
PCM2 input with the JP1 jumpers in 
place would result in turning on PB1 
and NB1 and counter-clockwise rota- 
tion of the brushed DC motor's shaft. 
Thus, with the JP1 jumpers populated, 
we combine the pair of half-bridges 
into a full H-Bridge with all of the safe- 
ty features we designed still intact. 

In our simplified half-bridge 
brushed DC motor driver scenario, the 
PWM signal is applied to the NCM1 or 
NCM2 inputs. Since PWM1 and 
PWM2 are both tied logically high, the 
alternating PWM signal presented to 
the NCM1 or NCM2 inputs will force 
the MOSFET gates of NA1 or NB1 to 
chop the brushed DC motor's ground 
path relative to the duty cycle of 
the incoming PWM signal and thus, 

SERVO 07.2006 53 

Building (H-)Bridges — Part 1 



R12 74HC00 

jp12 4 











2. D1-D2 = BAT54S 

3. 74HC00-74HC08 VCC = PIN 14 

4. 74HC00-74HC08 GND = PIN 7 

5. TC4467-TC4469 VDD = PINS 15,16 

6. TC4467-TC4469 GND = PINS 7,8 

7. VCC = +5VDC 

8. DRIVE VOLTAGE >= +5VDC <= +12VDC 

SCHEMATIC 2. Not one, not two, not 
three, but four half-bridges and a regulat- 
ed +5 VDC power source to boot! Before 
_ this is all said and done, I'll show you . 
how to put all of these half-bridges to 
work in various configurations. 

regulate the motor shaft's speed. 

In most real-world cases, the 
PWM signal emanated by the micro- 
controller will be continuous as the 
programmer will simply kick off the 
microcontroller's PWM engine and 
only manipulate the PWM duty cycle 
as needed. With the PWM running 
continuously, most likely a full H- 
Bridge configuration will be used and 
the NCM1 or NCM2 inputs are then 
used as gates to allow or disallow the 

,e L 








10 l_Llo( 

9 , V 


J3 R9 





> R7 

> 0. 10 


JR1 r^ C 
^ D5 







(7^ ^' 






v ri 












PWM signal from passing on to the N- 
Channel MOSFET gates. 

Schematic 2 utilizes the rest of the 
gate logic inside all of the ICs that 
make up the four half-bridges. The 
TC4467 and TC4469 can be powered 
by the standard logic supply of +5 VDC 
or by the DRIVE VOLTAGE, which can 
span from +5 VDC to +18 VDC. A 
jumper on JP3 determines which sup- 
ply the TC4467 and TC4469 draw their 
power from. If you're scratching your 
head as to why I haven't mentioned 
the 0.10 ohm sense resistor, don't 

worry. I've got plans for that guy. 

The H-Bridge Hardware 

Enough theory ... let's build some- 
thing! I've assembled all of the compo- 
nents in Schematics 1 and 2 into the 
dual H-Bridge hardware you see in 
Photo 1 . The printed circuit board itself 
is an inexpensive double-sided board 
with a ground plane covering the entire 
non-component side. There are so few 
components that comprise the dual H- 
Bridge circuit that you can actually 
build this whole thing up by looking at 
the component placement in Photo 1. 

The H-Bridge circuitry you see in 
Photo 1 can be more easily under- 
stood when broken down into its com- 
ponent parts. Photo 2 details the anti- 
smoke logic and the TC4467/TC4469 
MOSFET drivers. From left top to right 

PHOTO 1. There are actually four half- 
bridges buried within this mix of logic and 
MOSFET drivers. You can run this baby as 
four independent half-bridges or a pair of 
full H-Bridges. In addition to being able to 
drive small motors with ease, the circuitry 
boasts some simple logic that prevents you 
from accidentally letting the magic smoke 
out of the MOSFETs and their drivers. 

54 SERVO 07.2006 

Building (H )Bridges — Part 1 

top, you see the power indicator LED 
and its respective current limiting 
resistor. Directly to the right of the 
power indicator LED/resistor combina- 
tion is JP1 which, when jumpered, 
puts half-bridges 1 and 2 (or Drives 1 
and 2) into a single, full H-Bridge con- 
figuration. JP2 — whose jumpers put 
Drives 3 and 4 into full H-Bridge mode 
— is positioned to the right of JP1 . 

Photo 3 is a bird's-eye-view of the 
H-Bridge +5 VDC logic power supply. 
There's nothing fancy here as the dual 
H-Bridge logic power supply is con- 
structed around an LM340S-5.0 fixed 
voltage regulator. The logic power 
supply always powers the 74HC00 
and the 74HC08 and can be jumpered 
to supply +5 VDC power to the 
MOSFETs, TC4467 and TC4469. The 
Drive Voltage jumper — which is just 
below the logic power supply — can 
also be positioned to provide the volt- 
age at the input of the LM340S-5.0 to 
the MOSFETs, TC4467 and TC4469. 
The Drive Voltage jumper is set across 
the +5 VDC position in Photo 3. 

The 10 pF EMI (Electromagnetic 
Interference) capacitors, the BAT54S 
made up of a pair of back-EMF steer- 
ing diodes, and the IRF7309 MOSFET 
pair are all packed into the electronic 
components you're close up on in 
Photo 4. All of the IRF7309 MOSFET 
drains (pins 5, 6, 7, and 8) are tied 
together and bonded to a one-square- 
inch heatsink/drive output pad. The 
heatsink size is directly proportional 
to the amount of current you want to 
pull through the bridge's MOSFETs. 

Crossing the Bridge 

I've provided the dual 
H-Bridge ExpressPCB layout 
file — which is available on 
the SERVO website (www. — for 
those of you that may wish to 
customize the H-Bridge design 
I've presented or simply order 

PHOTO 3. Imagine that ... a 
National Semiconductor fixed 
voltage regulator providing 
regulated power to the logic. The 
screw terminal in this shot is the 
portal for incoming power for the 
dual H-Bridge logic and motor. 

PHOTO 2. There are 16 
logic gates and eight 
MOSFET drivers in this 
shot. Note the bridge 
control inputs pinned 
out to the left and the 
bridge configuration 
jumper blocks, which are 
bare indicating half- 
bridge mode. The dozen 
10K resistors surrounding 
the bridge configuration 
jumper blocks guarantee 
that the MOSFETs are 
turned off in the absence 
of input stimulus at the 
bridge control inputs. 

your own set of dual 
H-Bridge boards from 
ExpressPCB directly. 
For those of you that 

are surface 
mount challenged, you can also get all 
of the SMT components that make up 
the dual H-Bridge I've described as 
through-hole and DIP packaging, with 
the exception of the IRF7309 MOSFETs. 
There's nothing to stop you from using 
MOSFETs that are packaged differently 
than the IRF7309s. 

If you haven't skipped through 
the pages to get here, you've made it 
to the end of this part of our H-Bridge 
discussion. You now know how to 
control each and every one of the 
MOSFETs on all four half-bridges and, 
once you build up the H-Bridge circuit 
I've offered to you, you can attach a 
brushed DC motor and jumper in the 
bridge control logic levels necessary 
to make the motor shaft spin in a 
clockwise or counter-clockwise direc- 
tion. If you already have the means 
and knowledge to do so, you can also 
present a PWM signal to the proper 
bridge control inputs and control the 

speed of your motor's shaft. 

Although we've crossed the 
"bridge," we're not done. Next time, 
I'll introduce you to the brand new 
PIC16FHV616 and show you how to 
use simple PIC assembler code to 
exploit all of the PIC16HV616's special 
functionality to drive stepper and 
brushed DC motors with the H-Bridge 
circuitry you've just read about. I'll also 
produce some circuitry and firmware 
to put that 0.10 ohm sense resistor to 
work as a vital component of a safety 
net and motor current monitor station 
for the H-Bridge MOSFETs. 

Peter Best can be contacted via 
email at 

PHOTO 4. Here's a complete half-bridge, 
including the back-EMF steering diodes 
and the EMI capacitors. The IRF7309 was 
designed to switch things about in laptop 
computers and other electronic devices 
that require higher switching currents from 
smaller footprint components. 

SERVO 07.2006 

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56 SERVO 07.2006 

In the past, this column has shown 
you how to generate sounds through 
synthesis and how to generate speech 
from plain old ASCII text. This month, 
you'll see how easy it is to add audio 
recording and playback capability to 
your robot. If you have ever wanted to 
have your robot play old sci-fi sound 
effects or possibly cry out for help 
when it encounters a situation that it 
can't deal with, then this is the column 
for you! 

Play It Again 
and Again 

A company called Winbond 
produces chips that let you record 
and play back audio. With the chips in 
their ChipCorder line, you will be 
able to record up to 16 minutes of 
audio for later playback. Many of 
these chips have been available for 
years and are readily available from 
places such as Digi-Key. These chips 
are capable of producing audio at 
frequencies of up to 3.4 kHz (with a 
sample rate of 8 kHz) so they won't 
be able to produce high-pitched 
sounds, but will do fine with most 
sounds that you would like to play 

Meet the 

The chip that this column will 
discuss is the ISD4003-04MP. It can 
play back up to four minutes of audio 
with a sample rate of 8 kHz. It has 28 
pins and is packaged in a DIP package 
that is .6" wide. The ISD4003 requires 

very few external parts in order to 
record and play back. 

For the most part, all you will need 
are a few capacitors. This chip has an 
internal clock to control the speed of its 
recording and playback that is accurate 
to within -6% to +4% of the needed 
frequency over a large temperature 
range, but if you require higher 
precision or simply need your audio 
to remain in perfect sync with your 
application, then you can provide an 
external clock source. 

You can communicate with the 
ISD4003 using only four pins. These 
pins are a slave select pin and three 
SPI (Serial Peripheral Interface) pins. 
There are two other pins that you 
might be interested in using. These 
pins are the 'row address clock' pin 
and the 'interrupt' pin. Internally, the 
ISD chip has a large 2D array of analog 
Flash cells. This is something of a novel 
technology since most Flash devices 
store only high and low values 
that correspond to a one or a 

Internally, the ISD chip 
doesn't use compression to be 
able to store all of the sound, 
it just writes the sounds 
directly to the analog Flash. 
The ISD's Flash memory is 
arranged into rows and 
columns. During playback, 
every time that it reaches the 
end of a row, the row address 
clock pin will drop low for 25 
milliseconds. On a chip that 
has a sample rate of 8,000 Hz, 
these interrupts happen every 
1/5th of a second. 

Pin Interrupted 

The other pin that you might be 
interested in is the interrupt pin. This 
pin will drop low when the end of a 
recording is reached during playback. It 
will also go low during recording if you 
fill up the memory of the chip. Using 
the interrupt pin allows you to do other 
things while the chip is playing. If you 
want to know when a sound is done 
playing, you can monitor the interrupt 
pin, otherwise you will need to monitor 
the row address clock or just delay for 
the amount of time that it takes to play 
your sound. 

Chip Basics 

Let's get to the basics of how this 
chip works. As mentioned earlier, this 
chip communicates with an external 
processor using SPI. SPI uses two 
data lines and a clock line. Typically, a 

Figure 1. The pinout of the ISD4003 chip. 





MOSI| 2 

27 iVr.nn 



V SSD I 4 

25 IINT 

NCI 5 

24 |RAC 


23 |V S sA 

22 INC 

NCI 8 

21 INC 


NCI 9 

NCI 10 

19 INC 

VsmI 11 

18 IVncA 


VssaI 12 


16 |ANAIN- 

AM CAP I 14 

15 INC 

SERVO 07.2006 57 

Rubberbands and Bailing Wire 



sclk ruuuuuuuuuuuuuuin 

MOSI |A0|Al|A2|A3|A4|A5|A6|A7|A8|A9|ft1Q|CQ|ci|C2|C3|c4 

MISO |cm^om|pq|pi|P2|P3|P4|P5|P6|P7|P8|P9^1Q| | | | — 

Figure 2. The data that is sent and received 
from the ISD chip. 

fourth line is also used. This line is 
usually called Chip Select (CS) or Slave 
Select (SS). The two data lines are 
usually labeled MOSI and MISO. 
These stand for Master Out Slave In 
and Master In Slave Out. The master 
is the chip that generates the clock 

In essence, SPI hardware is really 
just two shift registers. One that 
data is clocked out of and one that 
data is clocked into. The register 
that shifts data to the master latches 
its data when the slave select line 
drops low, and the latch that 
receives data from the master latches 
its data when the slave select line 
goes high. 

To use the SPI port on the ISD4003 
chip, you will need to do the following: 
When you want to communicate 
with the ISD chip, you should drive 
the SS line low. This tells the chip 

that you are about to 
communicate with it. 
You will now start 
driving your clock line 
high and low. You need 
to write your data to 
the MOSI line when 
the clock is low and 
read data from the 
MISO line when the 
clock is high. 
When you are done sending and 
receiving data from the chip, you will 
drive the slave select line high. All com- 
mands to the ISD are 16 bits in length. 
This is convenient if your processor 
happens to have a hardware SPI port 
on it. With two writes to the SPI port, 
you can send one command and leave 
your processor free to do other things. 
If you don't have an SPI port, then 
communication is still pretty easy to do 
with software. 

Figure 2 shows a diagram of the 
signals needed to communicate with 
an ISD chip. As you can see, there are 
1 1 address bits and five control bits in 
each packet. The address bits are sent 
first and specify which row you would 
like to set the playback pointer to. 
There are 1,200 rows inside of each 
ISD4003 chip, so addresses of zero 
to 1,199 are possible. Figure 3 shows 
the list of commands that you can 

Command Address (11 bits) C ocTc2C3C4 Description 


Doesn't matter 


Power up: Device will be ready for an 
operation after Tpud (power up delay). 


Address (0-10) 


Plays from the address given. 


Doesn't matter 


Plays from the current location. 


Address (0-10) 


Records from the address given. 


Doesn't matter 


Records from the current location. 


Address (0-10) 


Initiates message cueing from the 
address given. 


Doesn't matter 


Performs message cueing from the 
current location. Proceeds to the end 
of the message. 


Doesn't matter 


Stops the current operation. 


Doesn't matter 

X1 0X0 

Stops the current operation and enters 
into standby (power down) mode. 


Doesn't matter 


Read the interrupt status bits: Overflow 
and EOM. 

Figure 3. The messages that can be sent to the ISD4003 chip. 

send to the ISD4003. 

Putting the 
ISD4003 to Use 

You now know all of the 
commands and how to send them. 
Let's look at what you need to do to 
actually use this chip. All of the timing 
described here is for a chip that has a 
8,000 Hz sample rate. There are some 
odd delays that you will need to take 
into account when using this chip. To 
play back when the chip is powered 
down, you will need to send the 
'powerup' command and then wait 
25 milliseconds. Send the 'setplay' 
command with the address that you 
want playback to start from and then 
send the 'play' command. You will 
now hear whatever you have record- 
ed at that location. The ISD chip will 
continue to play until it gets to the 
end of the recording or the end of 
memory in the chip. If you want to, 
you can send the 'stop' command to 
stop the playback. 

Recording is done a little different- 
ly. You will need to send the 'powerup' 
command twice to enter recording 
mode. The first time, you will need to 
wait 25 milliseconds. After the second 
time you send the 'powerup' 
command, you will need to wait 50 mil- 
liseconds. Now send the 'setrec' 
command with the address that 
you would like to start recording 
from. Next, send the 'rec' 
command to start recording. 
When you are done recording, 
send the 'stop' command. 

As you can see, knowing the 
address is important for starting 
and stopping playback and record- 
ing. You can figure out the 
address by sending any command. 
At the same time that you are 
sending the command, the ISD 
chip will send two status bits 
corresponding to if playback or 
recording has hit the end of the 
memory (OVF) or the end of the 
recording (EOM). 

After these two bits will be 
the current address that playback 
is happening from. The remaining 
three bits don't mean anything. 

58 SERVO 07.2006 

Rubberbands and Bailing Wire 

The 'rint' command allows you to read 
the address and interrupt bits without 
affecting the state of the chip. 

Great! You are now almost ready 
to actually use this chip. The only 
thing left to do is to actually hook up 
the chip. Figure 4 shows the connec- 
tions that you will need to make to 
play audio. Make sure to use a 3V 
regulator with this chip. This is the 
only exotic part that you will need. 
You can make a 3V regulator using a 
LM317 voltage regulator and a few 
extra parts or by having a few diodes 
in series with the 5V regulator that 
you are likely to be using with your 

The 3V regulator is not absolutely 
necessary. These chips will run at 5V, 
but you will have better audio quality 
at the three volts that the data sheet 
recommends. The SPI pins are five-volt 
tolerant when running at 3V, so inter- 
facing with a processor that is running 
at 5V isn't a problem. 

The ISD chip has a small amplifier 
inside of it but if you need some real 
volume, you will need to connect an 
amplifier to its output. Figure 5 shows 
a circuit that amplifies the output. To 
get the audio data into the chip, you 
will need to connect things as shown in 
Figure 6. Using that circuit allows you 
to record from a source such as your 
computer's audio out connector. 

Wrapping It Up 

Adding the ability to play around 
with recorded audio can let you do fun 
things like make a robot that slowly 
sneaks around where you live and 
occasionally lets loose with some 
scratching sounds to tease your cats. 
You could add sound effects for 



Sells various chips by ISD. 


Information about the various 
ISD chips. 


To and from 
your processor. 


MQ?I| 2 


NCl 6 





*sd 12 

AunnuT| 13 




25 | INT 
~24H RAC 
2l]V SSA 
22 !NC 



1 uF 

Figure 4. The connections that you will need to play sounds. 

various things. For example, 
when your robot backs up, it 
could beep like a large truck 
does. You could also have it play 
knocking sounds when it reach- 
es a door. If you were really 
ambitious, you could record a 
bunch of individual words and 
give your robot a voice — your 
voice! What will you do? 

Figure 5, Here's how to amplify the audio. 

Audio in 





10 uF 

10 uF 

HZ> Audio out 

Figure 6* Here's how to get audio into the chip. 

ssri - 



MOSlf 2 

27 |V CCD 

MISOl 3 

VssdI — - — 


25 I INT 

NCI 5 

24 IRAC 

NCI 6 

23 IVsSA 

NCI 7 
NCI 8 


22 |NC 
21 INC 

NCI 9 


NCI 10 

19 I NO 

VssaI 11 


-,-, [ANAIN+ 


1 UFA 

v SSAl — !^— 


16 [ANAIN- 
^I5~1NC 1 '* 


uF Audio in 

(32 mV peak to peak) 

-!-.1 uh 


SERVO 07.2006 59 



The goal 

of this 


column is to 

provide a basic 


of the various 


logic techniques. 

There are a lot 

of powerful 



available today 

that are rarely 

considered by 

hobbyists — and 

even some 

engineers — 

because of 


You have to be 


with the idea 

and concepts of 


logic before you 

will be likely to 

employ them. 

Imagine a system where you sit 
at your computer and create a 
complicated digital circuit. Some 
simulations are run and they look good. 
You then press a button and the circuit 
becomes real. Such systems exist 
today and are actually very common. 
They use Field Programmable Gate 
Arrays (FPGAs), which are sometimes 
referred to as ASICs (Application 
Specific Integrated Circuits). These chips 
can replace a whole printed circuit 
board (or whole systems) of standard 
digital ICs (Integrated Circuits), with 
prices starting at around $10 to $15. 

Xilinx vs. CPLD 

We ended the last session with 
CPLDs (Complex Programmable Logic 
Devices). The Invert/AND/OR structure 
was shown to be flexible and powerful. 
However, there are problems with that 
approach. The first is that the number 
of Invert/AND/OR gates increases 
directly with the number of input and 
feedback signals. There has to be one 
for each input term. But, obviously, not 
all input signals and all feedback sig- 
nals are used for every logic function. 

On the average, only a very small 
percentage of these signals will be used 
for any given function. This means that 
there will be a significant amount of 
waste. In fact, it is not uncommon to 
use only 10% of the available Invert/ 
AND/OR gates on a CPLD. Since ICs are 
basically priced by the area of silicon 
used plus a fixed package cost, this 
makes larger and larger CPLDs more 
and more cost //^effective. 

The second problem was the 
problem of feedback from the output 
registers. While this was possible, it 
generally wasted an input/output pin. 

by Gerard Fonte 

Clearly, this is not efficient either. And if 
your design required a number of coun- 
ters, you easily run out of available pins 
quickly. This isn't very good as well. 

Enter the FPGA. In 1 986, the Xilinx 
Corporation developed a decidedly 
new approach. They buried a large 
number of very small PALs on a single 
chip with programmable interconnects. 
This allowed the direct connection of 
any point to any other point (discussed 
in further detail later) and eliminated 
the inefficient Invert/AND/OR matrix. 

For the actual PAL logic, they used 
memory logic (as described in this 
column in the March '06 issue of SERVO). 
This created identical delays regardless of 
the complexity of the logic. Finally, they 
took the programming off-chip. You did- 
n't program the chip - you programmed 
a standard memory IC (or a special one 
of theirs). At start-up, the Xilinx chip 
would automatically download the 
design from the memory into on-board 
SRAM (Static Random Access Memory), 
which took a fraction of a second, then 
disable the external memory and then 
proceed to operate as designed. 

This was a really big change. The 
off-board memory was typically an 
EPROM (Eraseable Programmable Read 
Only Memory) that was extremely com- 
mon. So, if there was a problem with 
the design, all you had to do was to 
erase the EPROM, fix the design, and re- 
program the EPROM with the new ver- 
sion. Hardware hadn't just become as 
easy to change as software. Hardware 
became software. It was the first large 
scale, re-programmable logic device. 

This characteristic can be very 
powerful. For example, your new 
Internet appliance can also be upgrad- 
ed via the Internet. Or, if your robot is 
acting up at a competition, you can 

60 SERVO 07.2006 

phone home for a hardware fix. 
Consider the possibilities. (Note that 
the removal of power automatically 
erases the on-board SRAM. The design 
must be re-loaded every time power is 

There are a number of different 
manufacturers of FPGAs today (see the 
References sidebar). Xilinx is the front 
runner — Altera, Lattice, Actel, 
QuickLogic, and others round out the 
field. Each has its own approach that 
they think is best. However, Actel and 
QuickLogic use what is called "anti- 
fuse" technology. This means that the 
devices are not re-programmable and 
maintain their design in the power-off 
state. Since FPGAs start at $10, few 
hobbyists will find it financially feasible 
to spend $10 every time they want to 
change their design, especially when re- 
programmable solutions are available. 

Since the FPGA architecture varies 
significantly from manufacturer to 
manufacturer, it is not possible to 
provide generic examples as was 
done with PALs and CPLDs. However, 
all FPGAs still have to perform the same 
three basic functions: logic, intercon- 
nection, and input/output. We'll use 
Xilinx examples for these (a somewhat 
arbitrary choice) with the understand- 

ing that other manufacturers perform 
these functions differently. 

Basic Xilinx 

Figure 1 shows the basic 
Configurable Logic Block (CLB) for a 
Xilinx 3000 series FPGA. It's somewhat 
simplified and there are special func- 
tions and limitations that will not be 
discussed. In general, you can see that 
it resembles a small, registered-output 
PAL (Programmable Array Logic) that 
was discussed last time. The PAL's 
Invert/AND/OR logic has been replaced 
with a memory look-up table. There are 
three groups of signals: logic inputs, 
control inputs, and I/O (Input/Output). 
The logic inputs are self-explanatory. 
The control inputs are relatively more 
extensive than with a typical PAL or 
CPLD (Complex Programmable Logic 
Device). The outputs — like the regis- 
tered PALs — can be driven from the 
logic look-up table directly or from the 
D-type flip-flops. These CLBs make up 
the core logic of a Xilinx IC and number 
from 64 to thousands on a single chip. 

Interconnecting these CLBs are 
"Routing Resources." These are strips 
of silicon that act like wires. Transistors 

are turned on to make a connection. 
There are "local" resources that 
connect to adjacent CLBs and there are 
"Long Lines" that run the length of the 
chip for making low-skew connections 
over wide areas of the chip. 

Then there is the general wiring 
matrix than consists of short segments 
of "wires" that interconnect via a small 
switching matrix. There is a matrix for 
every CLB. Note that with a fixed 
amount of routing resources, it is pos- 
sible to create a design that can't be 
routed. However, in practice, this is dif- 
ficult to do. And should that situation 
arise, a larger chip will solve the prob- 
lem by permitting a less dense design. 

There are also I/O blocks. These 
provide the actual interface between 
the IC and the outside world. These are 
programmable, too, and are not as 
basic as one might think. Figure 2 
shows a simplified drawing of a 3000 
series I/O block. As you can see, it's 
pretty complex for an I/O pin. Both 
the input and output signals can be 
registered or direct. The polarity of the 
output and three-state control line can 

FIGURE 1. A Configurable Logic Block (CLB) 
from a Xilinx 3000 series FPGA. Note that 
it is similar to a PAL with memory logic 
instead of an Invert/AND/OR matrix. 

INPUT 1 - 
INPUT 2 - 
INPUT 4 - 
INPUT 5 - 


CL0CK ■ 










F ^ 









F ^ 





G ^ 



SERVO 07.2006 61 






IN YERT | <- 
















be inverted. And there are separate 
clocks for the input and output. The 
"Fixed Selections" are those that are 
set at program time and cannot be 
changed during normal operation. 
But wait! There's more! There are 


FPGA Manufacturers 
'---'- •--list) 

Actel Corporatior 

Altera Corporation 
The MAX II development board 
for CPLDs includes a download 
cable that supports their FPGAs. 

Cost Is about $150. 

Atmel Corporation 

Lattice Semiconductor Corporation 

QuickLogic Corporation 

Xilinx Corporation 

additional Xilinx features available on this 
and other devices (but not all chips have 
all the features). This includes internal tri- 
state busses, the ability to use logic mem- 
ory as real memory, actual bulk RAM on 
board, output slew rate control, input 
switching-level control, and more. If you 
can do it with discrete ICs, chances are 
that you can do it better with an FPGA. 
Again, different manufacturers 
have different approaches and imple- 
mentations. But they all must address 
the I/O, logic, and interconnect issues 
in some manner. And they all have 
additional features that they think are 
useful and/or important for the design 
of digital circuits. 

Good News — 
Bad News 

It is useful to note that the Xilinx 
3000 series is a "mature" technology. 
It's been around for at least 15 years. 
The 4000 series and the other Xilinx 
FPGAs pack two 3000-type CLBs into a 
single CLB. The smallest 3000 series has 
64 CLBs and will replace about 20 stan- 
dard digital ICs (including counters and 
registers). Xilinx suggests that this is 
about equal complexity to the 2000-gate 


block from a Xilinx 
3000 series FPGA. 
The user has many 
more options and 
capabilities when 
compared to a PAL 
or CPLD. 

design. Cost for this 
IC is about $13. 
Newer families 

— like the Virtex 
and Spartan series 

— have gate-equiva- 
lent counts of 
300,000 and more 
with thousands of 
double-sized CLBs. 
This is about 150 
times larger and 
can replace about 
3,000 standard dig- 
ital ICs. That's a 
whole system on a 
chip! The unit cost 
for the Spartan-IIE 
X2CS300E is under 
$40. (It now 

becomes abundantly clear why design- 
ing with standard digital ICs is no longer 
being employed by manufacturers.) 

Unfortunately, designing with 
FPGAs requires software. Naturally, this 
software is proprietary and can be quite 
expensive (several thousand dollars or 
more). That may not be a problem for 
a manufacturer who can recover that 
expense from the savings of a single 
design, but it's not a practical price for 
most hobbyists. The good news is that 
these manufacturers realize that it's 
important to provide entry-level systems 
so that students and small companies 
can gain familiarity with their products 
at low cost. They are in the business of 
selling ICs — not software. 

Cheap or free software systems 
are available that will allow the user to 
program at least some of the smaller 
parts. Typically, these introductory sys- 
tems do not provide all the advanced 
features of the full-priced software, but 
they are certainly adequate for the 
hobbyist and student. (Note that this 
software is almost always available as a 
download from a website or on a CD. 
Typically, the software consists of hun- 
dreds of megabytes of files. So, if you 
have a slow modem, opt for the CD.) 

62 SERVO 07.2006 

In addition to the software, some 
sort of programming hardware is also 
needed. Again, there are the profession- 
al (and expensive) devices and the cheap 
introductory accessories. Often times this 
is called a "Download Cable." Download 
cables are usually about $100. However, 
before you buy anything, it is very useful 
to talk to a sales representative. You 
can usually find them by referencing the 
manufacturer's website. 

Find out exactly what you need. 
Many times there are evaluation 
boards or kits that provide all the basic 
requirements (software and download 
cable) and are also extremely useful 
in providing a learning platform. 
Sometimes the cost of these evaluation 
boards is equal to (or at least close to) 
the download cable alone. 


There are several methods of get- 
ting your design into the system. The 
traditional way is with a schematic. This 
is generally supported with a variety 
of file formats. Most FPGA software 

systems include a schematic editor with 
a library of parts. This is very convenient 
and useful. However, surprisingly, some- 
times the library parts are not optimized 
for the FPGA. This can result in wasted 
resources which ultimately leads to 
slower and more costly designs. 

The other method is with the use of 
VHDL, Verilog, ABEL, or one of the other 
hardware programming languages. 
Again, an editor is usually provided for 
at least VHDL. (If not, downloads from 
the Web can usually be found.) 

It should be noted that using 
VHDL or other language for hardware 
design is not as simple as it may initial- 
ly appear. Subtle variations can creep in 
if the designer is not on-guard (a trans- 
parent latch instead of a D flip-flop, for 
example). Such variations can be 
extremely difficult to identify later. 

Additionally, the software approach 
doesn't define the hardware until com- 
pilation time. Sometimes the designer 
may not have a clue to the real size of 
the design until it's completed. It may 
be too large to be practical. 

Lastly, ordinary computer software 

is linear. One thing happens, then 
another thing, etc. Hardware operates 
in parallel with many operations 
occurring simultaneously. VHDL looks 
like computer software and it's easy to 
forget that it isn't. You can't debug 
VHDL with a linear frame of mind. 
Note that VHDL is a very useful and 
powerful tool. But it is different from 
the way most hardware designers 
work. It's important to understand 
these differences from the start. 


FPGAs are the pinnacle of program- 
mable logic. They provide a flexibility, 
complexity, and cost effectiveness that 
cannot be matched with any other off- 
the-shelf component. There are many 
manufacturers and many approaches 
to both the hardware and design 
software. Introductory systems are usu- 
ally available at a modest cost that are 
suitable for many lower-level designs. It 
is useful for any hobbyist or engineer to 
understand the capabilities and charac- 
teristics of these devices. 

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SERVO 07.2006 63 




J7 Bfgifi^. 

1 vJ J Ifv^w ^^^^^^^^^^B 

r r^ 


y Dan Kara 1 

j^iLjj 9; 

ilks, Coolness Walks 

In the robotics industry, "cool" ana "career" are m 
mutually exclusive. However, before you make your robotics 
career decision, be sure you are placing your bet on markets 
and companies that know how to make or attract money. 

Last month, we explored the 
subject of a career in robotics. 
The point was made that it 
makes little sense to discuss a robotics 
career without first defining or catego- 
rizing the robotics market. To that end, 
I broke the robotics industry into two 
major groups — Industrial Robotics and 
Service Robotics. Service Robotics was 
further subdivided into Professional 
Service Robotics, exemplified by 
technology such as surgical robots and 
military robots, and Domestic Service 
Robotics, those robots that find use in 
the home. Classes of domestic service 
robots, or if you prefer personal 
robots/consumer robots, include 
education/hobbyist robots, home 
care/lawn care robots, entertainment 
robots, smart toys, and home assistance 
/assistive robots. 

While defining the market is a 

64 SERVO 07.2006 

necessary first step in any career deci- 
sion process, it is only a start. You can 
also apply a taxonomic framework to 
buggy whips, but I would not want to 
base a career on that market. It is also 
necessary to determine if the market is 
"real." Market "reality" can be deter- 
mined in any number of ways. One of 
the best is quantitative market research 
data. Unfortunately, while quantitative 
data for the industrial robotics market 
is numerous and robust, the same 
cannot be said for the service robotics 
market. Research is particularly weak in 
the area of consumer robotics. 

Money Talks 

How can the robotics industry out- 
side of industrial robotics be validated 
given the lack of market sizing figures? 
There is one reality check that trumps 

all others. How can I put this without 
being blunt? Actually, there is no way 
so here goes ... it is all about money. 
There, I said it. Money. No matter how 
cool robots and robotic technology is, 
no matter how many robotics pieces 
you have seen on the Discovery 
Channel, and no matter how many 
competitions and science fair projects 
you might have participated in, when it 
comes to careers and career decisions, 
it is all about the money. 

Don't get me wrong. I am not 
advising that someone pursue or 
bypass a career based solely on the 
amount of money they can make. 
That approach is unwise and usually 
unfulfilling. There is a reason why the 
old adage "do what you love and the 
money will follow" continues to hold 
true for each new generation coming 
into the job market. 

Remember, robots will come into common usage if 
they can perform a function or service that cannot 
be performed by humans, or if they can do it more 
effectively or more cheaply than humans" 

No, when I speak of money I am 
concerned with an industry/company 
making money or securing investment 
dollars. Before anyone agrees to work 
for a robotics company they should ask 
themselves "does this company offer 
products and services that deliver real 
value to their customers, makes their 
customers money, or saves them 
money?" If you cannot answer "yes" to 
any of these questions, it would serve 
you better to continue your search for 
a robotics employer. 

Reading Between 
the Lines 

The good news is that the robotics 
industry is generating investment, 
products, and revenue. That is, the 
money is there. Judge for yourself. 
Following are just a couple of the 
announcements that came across my 
desk in a four week period in May- 
June. Most are straightforward, but 
hidden within each is the larger 
message as to where the hot markets 
in robotics are and why these 
companies will continue to prosper. 

On May 18th, VideoRay of 
Phoenixville, PA — a maker of Micro 
Underwater Remotely Operated 
Vehicles (Micro ROVs) — announced 
that their VideoRay Pro III product has 
been delivered to Monterey Bay 
Aquarium. The announcement — which 
described how the robot would be 
used to clean tanks and capture fish — 
was fairly vanilla. Hidden in the 
announcement was the fact that the 
Micro ROV would save the expense of 
mobilizing divers for many common 
aquarium procedures. 

Remember, robots will come into 
common usage if they can perform a 
function or service that cannot be 
performed by humans, or if they can 
do it more effectively or more cheaply 
than humans. While the VideoRay 

Micro ROV might not perform any 
better than a diver, their lower cost 
of operation makes the robot a good 
business choice. 

Companies that have diversified 
product lines protect themselves from 
downturns in specific markets. iRobot 
(Burlington, MA) illustrates this perfect- 
ly. The company recently announced 
that they have sold over two million of 
the little robot vacuums through over 
7,000 retail stores, including Target, 
Linens # n Things, Best Buy, Sears,, and Bed, Bath & 
Beyond, since they were introduced in 
2002. Roombas retail for $1 50 to $330 
each, providing iRobot with plenty of 
revenue and a boatload of validation 
for the consumer robotics market. 

iRobot's military sales have also 
been strong. For example, a week after 
iRobot announced its two-millionth 
Roomba sale, it followed up by disclos- 
ing that they had been awarded a 
$64.3 million Indefinite Delivery- 
Indefinite Quantity (IDIQ) contract for 
iRobot PackBot EOD robots, spare 
parts, training, and repair services. 

The award was granted by the 
Naval Air Warfare Center Training 
Systems Division (NAVAIR) on behalf of 
the Robotic Systems Joint Project 
Office. The robots will be used to 
support US forces in Iraq, Afghanistan, 

and elsewhere, to identify and dispose 
of Improvised Explosive Devices (lEDs). 

Also in May, Foster-Miller 
(Waltham, MA) - iRobot's competitor 
in the small ground-based military 
robot market — announced that it has 
been awarded a $63.9 million IDIQ 
contract also from NAVAIR for their 
TALON robots, training, parts, and so 
on. This contract came on the heels of 
a contract awarded to Foster-Miller 
three weeks earlier for an additional 
$28 million that is part of a separate 
$257 million NAVSEA IDIQ contract for 
TALON EOD robots. 

Defense spending for robotics 
technology is not limited to ground 
vehicles. In fact, in the same May 
timeframe as the Foster-Miller contract 
win, Honeywell Defense & Space 
Electronic Systems received a contract 
for $61 million from the US Army's 
Future Combat System (FCS) program 
lead systems integrators Boeing 
and partner Science Applications 
International Corporation (SAIC). 

The contract was for the develop- 
ment of Class I Unmanned Aerial 
Vehicle Systems (UAVS). Class I UAVS - 
sometimes called micro UAVs — are the 
smallest of the four unmanned aerial 
vehicle classes in the FCS program 
(prototypes weigh in at about 35 
pounds). They are designed to hover in 

SERVO 07.2006 

the air providing reconnaissance and 
surveillance capabilities to soldiers on 
the ground. 

The unmanned aerial vehicles 
market — of which micro UAVs is only 
a tiny component — is perhaps the 
largest robotics market of all. We have 
all seen full-size UAVs — such as the 
General Atomics Aeronautical Systems' 
Predator and Northrop Grumman's 
Global Hawk at work in Afghanistan 
and Iraq. These are big budget items in 

the robotics industry, but relatively 
cheap in terms of military aircraft. 
Therein is their appeal. Not only do 
UAVs exhibit an extremely high mission 
effectiveness rating, they are much 
cheaper to purchase, fly, and maintain 
that manned aircraft. 

Corrections in the Military 
Robotics Market? 

While the military robotics market 


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The technology builder's source for kits, components, supplies, tools, books and education. 

is going gangbusters now, there is 
always the possibility that there might 
be a downturn. Some analysts are 
already projecting that the defense 
industry will go into a correction when 
funding and sales begin to decline in 
the latter part of this decade. The logic 
goes that programs whose develop- 
ment and production were accelerated 
to deal with the war on terrorism in 
Afghanistan and Iraq will decline after 
they have reached completion. 

A dramatic drop in spending on 
military robotics is a real possibility, and 
might impact the robotics industry as a 
whole. However, robots — unlike other 
types of military hardware — can have 
many civilian applications. For example, 
while unmanned aerial vehicles are near- 
ly exclusively used for military purposes, 
non-military uses of UAVs are being 
explored by many companies for use in 
a vast number of civilian applications. 

Cool Does Not 
Count for Much 

It should be noted that market 
downturns are not limited to the 
defense industry. Any industry — with 
the possible exception of the porn and 
healthcare industries — are subject to 
the vicissitudes of capitalism's invisible 
hand. The important things to look for 
are robotics companies and markets 
that are attracting investment or gener- 
ating revenue. Both sources of money 
are based on business and product 
plans that deliver value to customers, 
make them money, or save them 
money. In the real world of careers, 
kids, and mortgages, the fact that 
robots are cool counts for little. The 
great thing about the robotics industry, 
however, is that robots and robotics 
technologies are cool and solid busi- 
ness can be built around them. SV 

Dan Kara is President of Robotics Trends, 
the producer of the RoboBusiness 
( ) and 

RoboNexus ( ) 

conferences, and publisher of Robotics 
Trends ( ), an 

online news, information, and analysis 
portal covering the personal, service, 
and mobile robotics market. He can be 
reached at 

SERVO 07.2006 


It's Your Bag 

Have you ever been looking for a 
specific tool in your workshop — 
like a screwdriver — only to find a 
hammer, instead? Then 
you did the 

unthinkable — you hammered a screw 
into something. Ugh. What you need is 
a better tool storage system. What you 
really should get is an eight-inch 
Electrician's/Maintenance Tote (Model 
#22128) from McGuire-Nicholas®. 
A great transportable tool storage 

McGuire-Nicholas is a product 
label of the Rooster® 
Group. A well-known sup- 
plier of plastic storage sys- 
tems, suspenders, and back 
support belts for carpenters, 
electricians, plumbers, and 
other Do-lt-Yourself (DIY) 
workers, you can purchase 
McGuire-Nicholas products 
at your favorite home 
improvement supplier. For 
more information, go to www. 

Built from a rugged wear 

The McGuire-Nicholas 
Electrician's/ Maintenance Tote. 

material — that McGuire-Nicholas 
calls Toughwear™ — this tote sports 
over 30 pockets, loops, hooks, and 
latches for holding just about every 
robot-building tool that you own. 
Additionally, an included plastic parts 
organizer can be used for holding 
those small parts and fasteners that 
typically slide around and hide inside 
other tool storage bags. 

One feature that we really like 
about this tote is that it stands upright 
when placed flat on the ground. Then 
just push aside the oversized carrying 
handle and you have easy access to the 
four big pockets that are ensconced 
inside the tote's main body. 

If you're looking for a storage 
solution that is a little less vertical and 
more horizontal, the 14-inch Tool Bag 
with Plastic Tray (Model #22314) offers 
fewer loops, hooks, and latches, but 
more "super-sized" pockets for holding 
your batteries, wheels, and servo 
motors. All wrapped up in an easy to 
transport bag. 

My Other Parts 
Storage is a 
Porsche (Red) 

No matter what your level of 
involvement is with robotics — 
BEAM, combat, microcontroller, or 
LEGO® Mindstorms® — one thing is for 
sure, after about one year of building 
bots, you will have acquired a substan- 
tial warehouse of parts, components, 
and elements. Now your real problem 
arises ... where to store all of this stuff. 
It's not just a matter of ferreting 
your parts collection away in a set 
of plastic cubbyholes, you have ^ 
to be able to find the right part 
at the right time. What you need 
is a parts organizer storage system 

As the leader in the manufac- 
ture of tackle boxes, Piano Molding 
Company ( 
has over 50 years' worth of experience 
in designing practical and useful 
plastic storage systems. This experi- 
ence is readily apparent in their 
incredible Stow 'N Go™ product line. 

Starting with the single-sided Stow 
'N Go Organizer (5230), you will be 
able to segregate up to 27 different 
parts. Protected with a smooth-operat- 
ing snap closure system that Piano 
Molding calls Lock-Jaw™, this organizer 
has a clear hinged lid for quick "see- 
through" parts identification. Painted 
in a fancy color called Porsche Red, this 
impact-resistant organizer will make 
you feel like your components collec- 
tion is being transported in a Hummer. 

If you were raised on a tackle box 

however, the Stow # N 
Organizer (1354-20) wil 
instant familiarity check, 
like a tall tackle box, 

Go Pro Rack 

I give you an 

Looking a lot 

the Pro Rack 

The Piano 
Stow 'N Go. 

Organizer is actually four Piano 
Molding 3500 series StowAway® utility 
boxes housed inside a brilliant smoked 
plastic drop-front lid. Just flip two safe- 
ty latches, drop the front lid, and slide 
out one of the four utility boxes. Access 
to your beloved LEGO Technic elements 
has never been so easy. 

Additionally, there is an open bay 
storage bin located in the Pro Rack 
Organizer's lid. An oversized 
snap closure latch keeps this lid 
shut during transport. 

If you're one of SERVO 
Magazine's founding sub- 
scribers, then you have proba- 
bly amassed a much larger parts 
collection. Luckily, Piano Molding 
makes a couple of larger storage 
solutions (e.g., Stow # N Go Double 
Organizer; 5232 and Stow # N Go 
Pro Rack Organizer w/3600 boxes; 
1364-20) - just right for your "big 
boy" toys. SV 

SERVO 07.2006 67 

J> J 


Tune in eacft month for a heads-up on 

where to get all of your "robotics 

resources" for the best or ices! 



Robotic Arms 
and Grippers 

Imagine going through life with your 
arms in a straightjacket. Now 
imagine how your armless, handless 
robot feels — er, assuming it has 
feelings to begin with! Robots without 
appendages are limited to rolling or 
walking about, possibly noting things 
than occur around them, and little else. 
The more sophisticated robots in 
science, industry, and research have at 
least one arm for the purpose of grasp- 
ing, moving, or reorienting objects. 
Arms extend the reach of robots and 
make them more human-like. For all the 
extra capabilities they provide a robot, 
it's notable that arms and hands aren't 
too difficult to add. You can build your 
own, or purchase readymade solutions 
from a number of sources. 

This installment of Robotics 
Resources deals with the concept and 
design theory of basic robotic arms and 
grippers. We'll stay on the low end of 
the cost spectrum, suitable for use on 
smaller desktop and educational 'bots. 
We'll also consider as separate entities 
the arm and hand (or "gripper") mech- 
anisms. Each provide their own distinct 

A Look at 
Human Arms 

Consider for a moment your own 
arms. You'll probably notice a number 
of important points. First, your arm has 
two major joints: the shoulder and the 
elbow (the wrist, as far as robotics is 
concerned, is usually considered part 
of the gripper mechanism). Your shoul- 

68 SERVO 07.2006 

der can move in two planes — both up 
and down, and back and forth. The 
elbow joint is capable of moving in two 
planes, as well: back and forth, and up 
and down. 

The joints in your arm, and your 
ability to move them, are called 
degrees of freedom. Your shoulder 
provides two degrees of freedom in 
itself: shoulder rotation and shoulder 
flexion. The elbow joint adds a third 
and fourth degree of freedom: elbow 
flexion and elbow rotation. 

Robotic arms also have degrees of 
freedom. But instead of muscles, ten- 
dons, ball-and-socket joints, and bones, 
robot arms are made from metal, plas- 
tic, wood, motors, solenoids, gears, 
pulleys, and a variety of other mechan- 
ical components. Some robot arms 
provide just one degree of freedom. 
Others provide three, four, and even 
more separate degrees of freedom. 

Types of Robotic Arms 

In the world of robotics, arms are 
classified by the shape of the area that 
the end of the arm (where the gripper 
is) can reach. This accessible area is 
called the work envelope. For the most 
part, in the case of a mobile robot, 
the work envelope does not take into 
consideration motion by the robot's 
body, just the arm mechanism. 

The human arm has a nearly spher- 
ical work envelope. We can reach just 
about anything, as long as it is within 
arm's length, within the inside of about 
three-quarters of a sphere. In a robot, 

such a robot arm would be said to have 
revolute coordinates. There are three 
more, decidedly non-human robot arm 
designs: polar coordinate, cylindrical 
coordinate, and Cartesian coordinate. 
All of them support at least three 
degrees of freedom. 

As noted above, revolute coordi- 
nate robotic arms are modeled after 
the human arm, so they have many of 
the same capabilities. The typical 
design is somewhat different, however, 
because of the complexity of the 
human shoulder joint. 

In the revolute coordinate arm, the 
shoulder joint of the robotic arm is real- 
ly two different mechanisms. Shoulder 
rotation is accomplished by spinning the 
arm at its base, almost as if the arm 
were mounted on a turntable. Shoulder 
flexion is accomplished by tilting the 
upper arm member backward and for- 
ward. Elbow flexion works just as it does 
in the human arm. It moves the forearm 
up and down. Revolute coordinate arms 
are a favorite design choice for hobby 
robots. They provide a great deal of 
flexibility, and provide an appearance 
similar to that of the human arm. 

The work envelope of the polar 
coordinate arm is half-sphere shaped. 
Polar coordinate arms are among the 
most flexible in terms of being able to 
grasp a variety of objects scattered 
about the robot. A turntable rotates 
the entire arm, just as it does with a 
revolute coordinate arm. This function 
is akin to shoulder rotation. The polar 
coordinate arm lacks a means for flex- 
ing or bending its shoulder, however. 

fta&oTtCi Resources 

The second degree of freedom is 
the elbow joint, which moves the fore- 
arm up and down. The third degree of 
freedom is accomplished by varying the 
reach of the forearm. An "inner" fore- 
arm extends or retracts to bring the 
gripper closer to or farther away from 
the robot. Without the inner forearm, 
the arm would be able to grasp objects 
laid out in a finite two-dimensional 
circle in front of it. 

The cylindrical coordinate arm 
looks a little like a robotic forklift. The 
name is derived from the cylindrical 
shape of its work envelope. Shoulder 
rotation is accomplished by a revolving 
base, as in revolute and polar coordi- 
nate arms. The forearm is attached to 
an elevator-like lift mechanism. The 
forearm moves up and down this 
column to grasp objects at various 
heights. To allow the arm to reach 
objects in three-dimensional space, the 
forearm is outfitted with an extension 
mechanism, similar to the one found in 
a polar coordinate arm. 

The work envelope of a Cartesian 
coordinate arm resembles a box. It is the 
most unlike the human arm and least 
resembles the other three arm types. It 
has no rotating parts. The base consists 
of a conveyer belt-like track. The track 
moves the elevator column (like the one 
in a cylindrical coordinate arm) back and 
forth. The forearm moves up and down 
the column and has an inner arm that 
extends the reach closer to, or farther 
away from, the robot. 

Powering the Arm 

There are three general ways of 
moving the joints in a robot arm: 

• Electrical actuation is with the use of 
motors, solenoids, and other electro- 
mechanical devices. It is the most com- 
mon and easiest to implement. The 
motors for elbow flexion, as well as the 
motors for the gripper mechanism, can 
be placed in or near the base. Cables, 
chains, or belts connect the motors to 
the joints they serve. 

• Hydraulic actuation uses oil-reservoir 
pressure cylinders, similar to the kind 

used in earth-moving equipment and 
automobile brake systems. The fluid is 
non-corrosive and inhibits rust: both 
are the immediate ruin of any hydraulic 
system. Though water can be used in a 
hydraulic system, if the parts are made 
of metal, no doubt they will eventually 
suffer from rust, corrosion, or damage 
by water deposits. For a simple home- 
brew robot, however, a water-based 
hydraulic system using plastic parts is a 
viable alternative. 

• Pneumatic actuation is similar to 
hydraulic, except that pressurized air is 
used instead of oil or fluid (the air 
often has a small amount of oil mixed 
in it for lubrication purposes). Both 
hydraulic and pneumatic systems 
provide greater power than electrical 
actuation, but they are more difficult 
to use. In addition to the actuation 
cylinders themselves, a pump is 
required to pressurize the air or oil, and 
valves are used to control the retraction 
or extension of the cylinders. 

Note that electrical activation 
doesn't always have to be via an 
electro-mechanical device such as a 
motor or solenoid. Other electrically- 
induced activation is possible using a 
variety of technologies. One of particu- 
lar interest to hobby robot builders is 
shape memory alloy, or SMA. SMA 
material goes by a number of trade 
names, such as Bio-Metal, Dynalloy, 
Nitinol, and Muscle Wire. 

The construction of various SMA 
materials differs from manufacturer 
to manufacturer, but the activation 
technique is about the 
same: when heat is apply 
to the metal, it contracts 
to a pre-defined state. 
Heat can be applied 
directly, through a flame 
or with hot water, or by 
passing an electrical cur- 
rent through the material. 
Electrical activation is the 
most common technique 
used in robotics. 

A disadvantage of 
SMA is its slow expansion 
rate: the metal must cool 

before it relaxes and returns to its pre- 
heated shape and size. The larger the 
metal, the longer it takes to cool, so 
the slower the "muscle" returns to its 
non-contracted state. As a result, most 
of the shape memory alloy material 
you'll see available is hair-thin. Don't let 
the small diameter of the wire fool you, 
however. Muscle Wire, and many other 
SMA materials, can hold considerable 
weight — several pounds in both the 
contracted and non-contracted state. 

An interesting variation on pneu- 
matic actuation is the "Air Muscle," 
an ingenious combination of a small 
rubber tube and black plastic mesh. 
The rubber tube acts as an expandable 
bladder, and the plastic mesh forces the 
tube to inflate in a controllable manner. 

Air Muscle is available pre-made in 
various sizes. It is activated by pumping 
air into the tube. When filled with air, 
the tube expands its width, but con- 
tracts its length by about 25 percent. 
The result is that the tube and mesh 
act as a kind of mechanical muscle. The 
Air Muscle is said to be more efficient 
than the standard pneumatic cylinder 
and, according to its makers, has about 
a 400:1 power-to- weight ratio. 

A Closer Look at 
Robotic Grippers 

In the world of robotics, hands are 
usually called grippers, or end effectors. 
The word gripper better describes their 
function. Few robotic hands can manip- 
ulate objects with the fine motor control 
of a human hand. They simply grasp or 
grip the object, hence the name gripper. 

FIGURE 1* Robodyssey's Gripper mounted onto a 
mouse and holding a can with eight ounces of water. 

SERVO 07.2006 

RO&oTiCS KftOWCft 


In addition to the companies 
listed in this article, the following 
online sources resell arm and gripper 
kits made by OWI and/or other 
manufacturers, A few offer their own 
custom products: 


Gripper designs are numerous, and 
none are ideal for all applications. Each 
gripper style has unique advantages. 
Here are a number of useful gripper 
designs you can use for your various 
robots, but this list is by no means inclu- 
sive of all the gripper styles. As a quick 
note, the names I use to refer to the 
various gripper designs are descriptive 
only. You'll see a variety of terms used 
for these and other forms of grippers. 

Snap-Activated Lever (the "Clapper") 

The snap-activated lever is one of 
the simplest gripper designs. The grip- 
per is composed of two metal, wood, or 
plastic plates. The bottom plate is 
secured to the gripper body; the top 

plate is hinged. A small spring-loaded 
solenoid is positioned inside, between 
the two plates. When the solenoid is 
not activated, a spring pushes the two 
flaps out, and the gripper is open. 
When the solenoid is activated, the 
plunger pulls in, and the gripper closes. 
The amount of movement at the end of 
the gripper is minimal — about a half 
inch with most solenoids. However, that 
is enough for general gripping tasks. 

Variations include using a small 
motor instead of the solenoid. A 
solenoid provides for either open or 
closed positions, whereas a proper 
motor allows for positions in between. 
For example, by using a small R/C 
servo motor, it's possible to position 
the movable plate to various points. 
The movable plate is connected to the 
servo motor by way of a linkage. 


The pincher gripper uses two mov- 
able "fingers" that open or close, either 
from a common hinging point, or with 
a special joint that allows for parallel 
movement of the fingers. The benefit 
of the pincher is that both fingers close 
in around an object. This is generally 

FIGURE 2* Joinmax/MCIIRobot sells plastic robot kits, including an arm/gripper with 
six degrees of freedom. The arm is controlled by specialized servo motors. 

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We are the US marketing arm of Joinmax Digital, a digital technology company focusing on the development and 
manufacturing of affordable robotic toys and DIY (Do It Yourself) robot kit. With built-in programmable artificial 
intelligence (A.I,), our robotic toys are easy to program and require no previous computer science knowledge. 
The DIY robot kits hands-on approach will enable our customers to understand various aspects of robotics and 
artificial intelligences. They will learn how to put them together and manipulate their intelligence with an easy-to- 
learn programming language. 
We will be introducing the following three series of products: 

1. Robot pet: IQ BUG. 

2. Do-It-Yourself (DIY) robot kits: 



I" F F I" n«mternet 

preferred over the snap-activated lever, 
where one plate is fixed and the other 

The designs of pinchers can vary 
greatly. One common approach is 
to use a pull-rod at the base of the 
fingers. Pull on the pull-rod, and the 
fingers open; push on it, and they 
close. The action of the fingers is like 
the blades of a pair of scissors, which 
means for larger and rounded objects, 
there is a potential that the closing 
fingers will actually push the object 
away. This problem can be largely 
avoided by using fingers shaped in a 
semi-circle so that the fingers close in 
around the object more evenly. 

With a parallel joint, the fingers are 
parallel from one another throughout 
their entire in-and-out movement. A dis- 
advantage of most parallel pincher grip- 
pers is that they use straight fingers, 
which afford little contact area when 
grasping round and cylindrical objects. 

Flexible Finger 

Various designs are used to pro- 
duce a gripper with human finger-like 
appendages. The fingers are usually 
just segmented pieces of plastic, wood, 
or metal, with a thin flap for a hinge. A 
very thin strip of metal (sometimes 
plastic) is placed on the inside of the 
fingers. When the strip is pulled taut, 
the fingers close in. The strip is natural- 
ly springy, so when it's released, the 
fingers open back up. Several child toys 
have used this design principle, and in 
fact, such toys are often re-engineered 
for use on a homemade robot. 

Adding Wrist Rotation 

The human wrist has three 
degrees of freedom: it can twist on the 
forearm, it can rock up and down, and 
it can rack from side to side. You can 
add some or all of these degrees of 
freedom to a robotic hand. With most 
arm designs, you'll just want to rotate 
the gripper at the wrist. 

Wrist rotation is usually performed 
by a motor attached at the end of the 
arm or at the base. When connected at 
the base (for weight considerations), a 
cable or chain joins the motor shaft to 

70 SERVO 07.2006 

fta&oTtCi ReSouRCft 

the wrist. The gripper and motor shaft 
are outfitted with mating spur gears. 
You can also use chains (miniature or 
#25) or timing belts to link the gripper 
to the drive motor. 

Another possibility is a worm gear 
on the motor shaft. Remember that 
worm gears introduce a great deal of 
gear reduction, so take this into account 
when planning your robot. The wrist 
should not turn too quickly or too slowly. 

Yet another approach is to use a 
rotary solenoid. These special-purpose 
solenoids have a plate that turns 30-50 
degrees in one direction when power is 
applied. The plate is spring loaded, so 
it returns to normal position when the 
power is removed. Mount the solenoid 
on the arm and attach the plate to the 
wrist of the gripper. 


For those who wish to purchase a 
ready-made arm and/or gripper, there 
are a number of commercial enterprises 
that offer low-cost solutions. The follow- 
ing list is by no means exhaustive, but it 
should point you in the right direction. 

Budget Robotics 

My own small robotics manufactur- 
ing company, Budget Robotics offers 
several very low-cost grippers. Products 
include the Big Gripper, a scissor-style 
pincher gripper with formed fingers. 


Five- and six-axis robotic arms, 
operated by R/C servos. Crustcrawler 
kits are made from aluminum. 


US distributor of Joinmax kits — 
includes a robot arm and grip kit 
with six degrees of freedom. 
Resellers include, Garage- 
Technologies. com, and many others. 


Manufactures and sells numerous 
servo-based arm and gripper kits. 

FIGURE 3» Lynxmotion arm kits are made from sturdy polycarbonate. The company 
also offers brackets and hardware to make custom-designed, servo-operated arms. 

Parallax, Inc. 

Boe-Bot Gripper Kit, five-axis robot- 
ic arm (resold from Crustcrawler). 


Offers a low-cost, scissor-style, 
servo-operated pincher gripper. 

FIGURE 4* Robodyssey's gripper kit includes a servo and 
shaped parts to make a scissor-style pincher. 


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Robot Parts and Mechanical 

Robodyssey produces robots for education as well as the hobbyist. We understand that everyone has different goals and 
needs for their robots. This is precisely why we offer the following different mechanical parts for your robot. 

Click on each product image to learn more. 

Robot Parts and Mechanical 

3 I I | 

Gripper Kit (with Servo) 
Code: GKWS 
Price: $25.95 
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30 Internet 

SERVO 07.2006 71 






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57 17.6 
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Aluminum I 


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product photos are avail a 
on the SERVO website at 

Upcoming topics include SBCs and H-bridges, sensors, kits, and actuators. If you're a manufacturer of one of these items, please send your 
product information to: Disclaimer: Pete Miles and the publishers strive to present the most accurate 
data possible in this comparison chart. Neither is responsible for errors or omissions. In the spirit of this information reference, we encourage 
readers to check with manufacturers for the latest product specs and pricing before proceeding with a design. In addition, readers should not 
interpret the printing order as any form of preference; products may be listed randomly or alphabetically by either company or product name. 









Infared Sharp 

Distance GP2YOA2I 

Infared Sharp 

Distance GP2YOA2I 

Infared Sharp 

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2K 13 

I4K 20 





32K 21 

I4K 22 

I4K 22 

32K 21 

32K 21 

32K 21 

32K 21 

32K 21 

32K 21 

PICBasic or 
any other 






PICBasic or 
any other 


PICBasic or 
any other 









































Includes CdS Light Sensors 
and programs for light 
following and avoidance. 

Includes the Mini Atom Bot 
Board which supports most 
224.75 5V sensors and the Playstation 
2 controller remote control, 
programming cable. 

Includes the Mini Atom Bot 
Board which supports most 
213.80 5V sensors and the Playstation 
2 controller remote control, 
programming cable. 


Precision laser cut parts for 
durable construction. 

Includes Robodyssey Advanced 
Motherboard, batteries and 
battery pack, programming 


Includes PICPac Motherboard, 
batteries, and battery pack. 


Heavy-duty construction 
that is school tough; all 
documentation is curriculum 

Includes Robodyssey Advanced 
Motherboard, batteries and 
battery pack, programming 

Includes Robodyssey Advanced 

Motherboard, batteries and 
,r A m battery pack, Experimenters 
** b ' w Solderless BreadBoard, 

breadboard cables, standoff, 

programming cable. 

Heavy-duty construction that 
is school tough; all documenta- 
tion is curriculum based. 

Includes Robodyssey Advanced 
239.50 Motherboard, batteries and bat- 
tery pack, programming cable. 


Heavy-duty construction that 
is school tough; all documenta- 
tion is curriculum based. 

Includes one speaker, three 
programmable buttons, six 
LEDs, power supply for test- 
ing, compiler on a CD, 
newsletter on new applica- 
tions, remote control capable. 

#sg The SERVO Store 


Designing Autonomous 
Mobile Robots 

by John Holland 
Designing Autonomous 
Mobile Robots intro- 
duces the reader to 
the fundamental con- 
cepts of this complex 
field. The author 
addresses all the per- 
tinent topics of the 
electronic hardware 
and software of 
mobile robot design, 
with particular emphasis on the more diffi- 
cult problems of control, navigation, and 
sensor interfacing. Covering topics such as 
advanced sensor fusion, control systems for 
a wide array of application sensors and 
instrumentation, and fuzzy logic applica- 
tions, this volume is essential reading for 
engineers undertaking robotics projects, as 
well as undergraduate and graduate stu- 
dents studying robotic engineering, artificial 
intelligence, and cognitive science. $49.95 

123 Robotics Experiments 
for the Evil Genius 

by Myke Predko 

If you enjoy tinkering in 
your workshop and 
have a fascination for 
robotics, you'll have 
hours of fun working 
through the 123 experi- 
ments found in this 
innovative project 
book. More than just 
an enjoyable way to 
spend time, these 
exciting experiments also provide a solid 
grounding in robotics, electronics, and pro- 
gramming. Each experiment builds on the 
skills acquired in those before it so you devel- 
op a hands-on, nuts-and-bolts understanding 
of robotics - from the ground up. $25.00 

CNC Robotics 

by Geoff Williams 
CNC Robotics gives 
you step-by-step, 
illustrated directions 
for designing, con- 
structing, and testing 
a fully functional CNC 
robot that saves you 
80 percent of the 
price of an off-the- 
shelf bot - and that 
can be customized to 
suit your purposes exactly, because you 
designed it. Written by an accomplished 
workshop bot designer/builder, this book 
gives you all the information you'll need on 
CNC robotics! $34.95 

74 SERVO 07.2006 

Teach Yourself 

Electricity and 

Teach Yourself Electricity and 
Electronics — Fourth Edition 

by Stan Gibilisco 

Learn the hows and 
whys behind basic elec- 
tricity, electronics, and 
communications with- 
out formal trainins. The 
best combination self- 
teaching guide, home 
reference, and class- 
room text on electricity 
and electronics has 

been updated to deliver the latest advances. 
Great for preparing for amateur and com- 
mercial licensing exams, this guide has been 
prized by thousands of students and profes- 
sionals for its uniquely thorough coverage 
ranging from DC and AC concepts to semi- 
conductors and integrated circuits. $34,95 

The Official Robosapien 
Hacker's Guide 

by Dave Prochnow 
The Robosapien robot 
was one of the most 
popular hobbyist gifts 
of the 2004 holiday 
season, selling approxi- 
mately 1.5 million units 
at major retail outlets. 
The brief manual 
accompanying the 
robot covered only 
basic movements and maneuvers - the 
robot's real power and potential remain 
undiscovered by most owners - until now! 
This timely book covers all the possible 
design additions, programming possibilities, 
and "hacks" not found anyplace else. $24.95 

Anatomy of a Robot 

by Charles Bergren 

This work looks under 

the hood of all robotic 

projects, stimulating 

teachers, students, 

and hobbyists to learn 

more about the gamut 

of areas associated 

with control systems 

and robotics. It offers 

a unique presentation '' Hlfi V. Hales Meioren 

in providing both theory and philosophy in 

a technical, yet entertaining way. Reading 

Anatomy of a Robot is like having a robot on 

the operating room table. Crack open the 

pages and you'll be able to dissect a robot 

from head to toe. $29.95 

We accept VISA, MC, AM EX, and DISCOVER 

Prices do not include shipping and 

may be subject to change. 

Open-Source Robotics and 
Process Control Cookbook 

by Lewin Edwards 
In this comprehen- 
sive guide, experi- 
enced embedded 
engineer and author, 
Lewin Edwards, 
demonstrates effi- 
cient and low-cost 
open-source design 
techniques, covering 
end-to-end robot- 
ic/process control 
systems using Linux as the development plat- 
form (and also as the embedded operating 
system), with extensive information on free 
compilers and other tools. Specifically, the 
book targets development of real-time physi- 
cal system controls using Atmel AVR micro- 
controllers communicating with Linux-based 
PCs for overmonitoring. Code examples are 
given to provide concrete illustrations of 
tasks described in the text. The accompany- 
ing CD-ROM contains all the code used in 
the design examples, as well as useful open- 
source tools for robotics and process con- 
trol system design. $49.95 

Build Your Own 
Humanoid Robots 

by Karl Williams 

This unique guide to 
sophisticated robotics 
projects brings humanoid 
robot construction home 
to the hobbyist. Written 
by a well-known figure in 
the robotics community, 
Build Your Own Humanoid 
Robots provides step-by- 
step directions for six exciting projects, 
each costing less than $300. Together, 
they form the essential ingredients for 
making your own humanoid robot. $24.95 

101 Spy Gadgets for the 
Evil Genius 

by Brad Graham/Kathy McGowan 

Utilizing inexpensive, 
easily-obtainable com- 
ponents, you can build 
the same information 
gathering, covert 
sleuthing devices used 
by your favorite film 
secret agent. Projects 
range from simple to 
sophisticated and 
come complete with a 
list of required parts and tools, numerous 
illustrations, and step-by-step assembly 
instructions. $24.95 

To order call 1-800-783-4624 or go to our 
website at iArww.servomagazine.Gom 

Nuts & Volts CD-Rom 

Here's some good 
news for Nuts & 
Volts readers! 
Starting with the 
January 2004 issue 
of Nuts & Volts, all 
of the issues 
through the 2004 
calendar year are 
now available on a 

Nuts St Volts 

Volume 25, No. 1-12 


CD that can be searched, printed, and easily 
stored. This CD includes all of Volume 25, 
issues 1-12, for a total of 12 issues. The CD- 
Rom is PC and Mac compatible. It requires 
Adobe Acrobat Reader version 6 or above. 
Adobe Acrobat Reader version 7 is included 
on the disc. $29.95 

PIC in Practice: A Project-based 
Approach — Second Edition 
by David W. Smith 
PIC in Practice is a graded course based 
around the practical use 
of the PIC microcontroller 
through project work. 
Principles are introduced 
gradually, through hands- 
on experience, enabling 
students to develop their 
understanding at their own 
pace. The book can be 
used at a variety of levels 
and the carefully graded 
projects make it ideal for colleges, schools, 
and universities. Newcomers to the PIC will 
find it a painless introduction, while electronics 
hobbyists will enjoy the practical nature of this 
first course in microcontrollers. $29.95 

Robotics Demystified 

by Edwin Wise 

There's no easier, 
faster, or more practi 
cal way to learn the 
really tough subjects. 
Demystified titles are 
the most efficient, 
interestingly written, 
brush-ups you can 
find. Organized as 
self-teaching guides, 
they come complete with key points, back- 
ground information, questions at the end of 
each chapter, and even final exams. You'll be 
able to learn more in less time, evaluate your 
strengths and weaknesses, and reinforce 
your knowledge and confidence. $19.95 



Check out our online bookstore at for a complete 
listing of all the books that are available. 


Are you ready for 

some good news? 

Starting with the 

first SERVO 

Magazine issue - 

November 2003 - 

all of the issues 

through the 2004 

calendar year are 

now available on a 

CD that can be searched, printed, and easily 

stored. This CD includes all of Volume 1, 

issues 11-12 and Volume 2, issues 1-12, for a 

total of 14 issues. The CD-Rom is PC and Mac 

compatible. It requires Adobe Acrobat 

Reader version 6 or above. Adobe Acrobat 

Reader version 7 is included on the disc. 


Robot Builder's Sourcebook 

by Gordon McComb 






Fascinated by the 
world of robotics, 
but don't know how 
to tap into the incred- 
ible amount of infor- 
mation available on 
the subject? Clueless 
as to locating specific 
information on robot- 
ics? Want the names, 
addresses, phone 
numbers, and websites of companies that 
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From HomoSapien to RoboSapien 

Before R2D2 there was R1D1 

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SERVO 07.2006 75 

Technical Titans Face Off in Texas 

Corey Morris 

Fear Factor gives Dark 
.Pounder a flying lesson. 


A member of Team 

Dragon Robotics after 

winning the Rookie 

Driver Award. 

The only thing that could drown out the cheers of the 
crowd, was the clash of steel on steel. The smell was unearth- 
ly, as were the sights. Bent steel, burnt motors, shattered plas- 
tic, flaming butane, and ripped aluminum; all were forged into 
one great machination created simply to overload the senses. 
On February 4, 2006, 13 teams hauled their robots out 
to Mike's Hobby Shop to face off for the top prize at 
SWARC'S Most Extreme Robot Challenge. 

As always, safety was top priority 
and the staff made sure that the Robot 
Fighting League rules were followed to 
the letter. By the time all the robots 
were deemed safe according to the RFL 
guidelines, SWARC'S Most Extreme 
Robot Challenge was off to a smooth 
start. The schedule was simple: fight 
bots until 1:00 P.M., and then take a 
lunch break for 30 minutes. After the 
break, come back and finish the fight 
brackets to determine the winners. 

Though there was a slight shortage 
of larger robots, a round-robin configu- 
ration allowed for plenty of destruction. For the ants, a sim- 
ple double elimination format was used. All robots weighing 
over a pound fought in the 24' by 24' Texas 
Toad Tank, while the ants dished out dam- 
age inside of the 4' by 4' ant box. 

The ants (1 -lb max.) kicked off the Most 
Extreme Robot Challenge with 10 bots and 
tons of hits rounding out the class. In addi- 
tion to the usuals like Team Dark Forces' ver- 
tical spinner Dark Pounder were some new- 
comers like T.U.F.Ti.C.K. and Hungry Hungry 

Team Shiny Thing is ready 
for battle. 

two drum spinners met in the finals. 
Fear Factor of Team Probotics and 
the aforementioned Team Wapu's 
Hungry Hungry Hippo. After a great 
fight Hungry Hungry Hippo came 
out on top as Texas' 1 -lb champ. 

Four beetles (3-lb max.), two pushbots, and two spinners 
attended the event, but the group was hardly unexciting. The 
arrival of Dark Slayer — a titanium bladed spinner — assured 
plenty of carnage was to be had. In the finals, Dark Slayer 
came out on top by beating down Fear Factor Sr. — a vertical 
spinner with a 12-inch blade. 

Weblinks: • 

Who said robot builders 
were crazy? 

Hippo. After proving their worth in battle, 

One spinner, one rammer, and one dustpan made up the 
hobbyweight (12-lb max.) class at SWARC'S Most Extreme 
Robot Challenge. Fulton's Folly and Scoopula pounded it out 
in the finals after defeating Mad Puppy — a horizontal spin- 
ner with a screaming gasoline engine. 

In the Featherweight (30-lb max.) class, Team Probotics' 
flame-spewing Lexan lifter My Girl Robot faced off against 
Team Monster's horizontal spinner Metal Fatigue. Two fright- 
ening fights later Metal Fatigue came out on top, proving to 
be the tougher of the two. 

Crocbot, a past winner of many SWARC competitions, 
came out to protect his lightweight (60-lb max.) title against 
an all-steel wedge named Spinnerbait Jr. and the disk-wield- 
ing Guillotine. Three earth-shattering encounters left Crocbot 
on top for a third time, proving that, at the end of the day, it 
all comes down to how hard your shell is. 

If you want to see some great fights, meet some great 
people, and have a ton of fun, come down to Texas for 
SWARC's next event — the Texas Cup on September 9th. You 
won't be disappointed! 

Formed in 2000, the Southwestern 
Alliance of Robotic Combat began as a simple 
group of robot enthusiasts. Since then, the 
gathering has increased and includes people 
from greatly differing backgrounds. SWARC 
holds their events in Mike's Hobby Shop where 
builders can buy spare parts. Mike's Hobby 
Shop is also an ideal home for Fuzzy's Toad 
Tank, which is now being used by SWARC. 

76 SERVO 07.2006 

.. WbII, Almost 

by Jonathan £. Fant, P.E. 

These are exciting times for robot 
enthusiasts. It is hard to avoid 
robots. This summer, COG from MIT is 
residing here in Portland, Oregon 
(pronounced "ORE-UH-GUN" for you 
East Coast folks) at the Oregon 
Museum of Science and Industry. 

At least weekly there is an article 
in a newspaper or on TV regarding 
another robot (besides Honda's, that 
is). And, of course, the DARPA Grand 
Challenge was awesome this year. 

The next DARPA Grand Challenge 
promises to be even more exciting 
next year as autonomous vehicles 
move to the urban street environment. 

Locally, the IEEE Robotics group is 
sponsoring a software challenge in 
August to use video cameras in real time 
for indoor robot navigation functions. 

On the education front, the FIRST 
and LEGO-based competitions are 
exposing more students to robotics all 
the time. Almost every university and 
local community college has some form 
of robotics involvement, whether aca- 
demic instruction or a local student club. 

The present military value of 
robots is said to be enormous, even 
with the limited capabilities of today's 
machines. The US government is 
spending large amounts of money on 
new robot designs, so further advances 
are expected in military robots. 

Robots have become a national goal 
for many high-technology countries. 

Obviously, all the pieces are 
coming together for robots now. 
When I think about the slow progress 
from simple manufacturing arms of 

the 60's to where we have come 
today, it is obvious that a lot of 
technical progress has been made. 

These are definitely exciting times 
for robots! 

But Hold an Maw ... 

It is easy to get carried away in all 
the technical details and advertising 
hoopla. Almost none of the journalists 
have a clue about what a robot is from 
a technical point of view (the fine folks 
at SERVO being an obvious exception). 
Often the latest robot is touted as 
being a "break-through" when it is not. 
Are all of these machines really robots? 

Past authors of this column have 
discussed what a robot is and what is 
still lacking. Most readers of SERVO 
should already have a good idea 
of what a robot is, so I will give a 
condensed version in a moment. 

First, here is what a robot is not. 
Often robot definitions I have seen 
are similar to this: 

"A robot is a mechanical assemblage 
with moving parts and a controller, 
processor, or computer attached. " 

This is not an accurate definition 
since it includes just about everything 
made with moving parts, including 
your car and an elevator. 

Another definition often heard is 
intended to limit the type of devices 
on a control basis: 

"A robot is a mechanical assemblage 

with moving parts and a controller, 

processor, or computer attached that 

executes operations or movements 

with little or no human direction." 

This one is getting closer, but fails 
what I call "The Elevator Test," since 
you can substitute "elevator" for 
"robot" in the definition and still make 
a true statement. 

Something is 

So, something is still missing — 
something that we all intuitively know 
— that makes up the essence of a robot. 

First, let's distinguish between 
robots and robotic devices. 

Robotic devices include manufac- 
turing arms, automatic car wash 
machines, elevators, the Roomba and 
Scooba products by iRobot, and even 
your late-model car (or the SUV you 
are trying to trade in for a hybrid). 

So let's change the definition 
above to: 

"A robotic device is a mechanical 

assemblage with moving parts and 

a controller, processor, or computer 

attached that executes operations 

or movements with little or no 

human direction." 

As a definition for robotic devices, 
this one is pretty good, but does not 
define robots. 

So here is a short definition of a 

SERVO 07.2006 77 

"A robot is a robotic device that moves 

and operates in at least one existing 

real-world environment without tracks 

or guides and looks like a robot." 

The last part is not optional, since 
modern commercial aircraft are robotic 
devices that operate without tracks 
or guides. The "existing real-world 
environment" is intended to separate 
out special-environment machines. 

It is also circular and assumes one 
knows what a robot looks like. It does 
not state what part transforms the 
mechanical assemblage that looks like 
a robot into the true robot. 

So, I leave it to another time or 
others to perfect the definition of a 
true robot. But it does give us insight 
into what is needed — machines that 
operate in existing environments with 
little or no human direction. 

The Missing Parts 

Sensors and software are the parts 
that transform a robot-looking mechan- 
ical assemblage into a robot. Sensors 
are required to give surrounding envi- 

ronment information to the software. 

Without proper software, the 
hardware will look like a robot but 
remain a remote-controlled or pre- 
programmed puppet. 

Honda's robot comes to mind here. 
It definitely looks like a robot, but 
requires a human to program specific 
step sequences or operate it by remote 
control (my opinion based only on obser- 
vation since I cannot afford to buy one). 

If one assumes that existing sen- 
sors are adequate, then software 
becomes the only missing piece. More 
specifically, some form of machine- 
intelligence robot software. 

Certainly, all modern robot design- 
ers include software as a critical design 
component, but they typically focus 
in-depth on hardware, and then write 
just enough software to operate the 
hardware. This makes a great robotic 
device, but fails to make a robot. 

Robot software must be real- 
time aware of the local environment, 
including interacting with humans, and 
be goal-oriented to provide useful 
functions for humans. Obviously, the 
robotic device component (mechanics 

of the robot) must work under the 
direction of the robot software. 

Only when we focus on the 
machine-intelligence portion of our 
software will we finally build robots. 
We do not need to build C3P0 
software to get started, just enough to 
build safe, useful robots. 

This effort has already started. 
Stanford's DARPA team used a 
software-focused approach to win, the 
IEEE Video Odometry challenge 
(August 2006) focuses on a significant 
piece of the missing robot software, 
and the LEAF project (and others) are 
already underway. 

This is the age of robots ... now let's 
get busy and write robot software! 

Jonathan E. Fant, P.E. is president 
and founder of Future Robotics, Inc. 
( — a company 
dedicated to building real-world robot 
hardware, software, and accessories. 
He is an electrical engineer with a 
background in electrical power, 
controls, and robotics. He can be 
reached atjon @futurerobotics. com 

78 SERVO 07.2006 





O gain, I use the word Who in the title 
HH of my article, just as in my previous 
article about Robots Who Live With 
People in the April '06 issue of SERVO. 
I like the word, as it implies a closer 
relationship to a type of machine we all 
appreciate so much. However, there is a 
wide gap between living with and caring 
for a person — a difference that has been 
apparent for many millennia. 

Centuries ago, caring for a person 
who was disabled or ill usually meant 
keeping them comfortable in a bed and 
feeding them until they healed or died. 
Sometimes the "healing" process was 
worse than dying a peaceful death. 
Stretchers were used to move a sick 
person from one point to another. Later, 
as the science of medicine progressed 
and hospitals were developed to care 
for people, caring became more refined. 

Hospitals began to develop 
mechanical means to move or position 
a sick person instead of "man-handling" 
them about. Wheelchairs were the first 
of these devices, as the transport of an 
ill patient was very important. Later, 
manual lifts were developed to move a 
person from a bed to a wheel chair or 
rolling gurney, but human muscle 
power was still required. 

As the twentieth century pro- 
gressed, medical technology advances 
created powered patient lifts that rolled 
along on overhead tracks. A sling was 
placed around the patient and an over- 
head electric winch and cable attached 
to the sling allowed a nurse to lift the 
person out of a chair, bed, toilet, or 
bath. The winch was attached to the 
overhead track and a person could 

move the patient anywhere the tracks 
were mounted by just pushing the 
person along with their hands. Figure 1 
shows such a patient lift in use. 

A person is usually still required to 
operate the lift and move the patient 
along the overhead track — much like a 
butcher moving a side of beef in the 
cutting room. Powered wheelchairs 
and scooters allow people with disabil- 
ities to move about on their own — a 
joystick is at the end of one armrest 
controlling the direction and speed of 
the chair. However, when the disability 
is great enough, a person is sometimes 
required to move the patient into and 
out of the wheelchair and into a bed, 
bath, or toilet. At this point, the person 
loses their ability to live independently. 
Figure 2 shows an electric lift that is 
attached to the side of stairs to assist 
people in climbing stairs. 

A Robot to Assist 
People in Daily Life 

Living independence is a situation 
that I have examined thoroughly. Several 
years ago, my son Tom was severely 
injured when he was in the 
Navy and required constant 
attention for all of his basic 
needs. He had been a physical- 
ly fit Navy Seal candidate, but 
was reduced to helplessness 
after an accident. Fortunately, 
this condition passed after six 
months or so, but I had been 
thinking about what type of 
robot I could build that would 
attend to his needs. 

At about the same time, my sister 
Liz was slowly becoming an invalid due 
to a neurological disease and would 
require an entirely different type of 
care — robotic or otherwise. Just what 
kind of robot could I develop that 
would satisfy both of their needs? 
There are so many different types and 
degrees of disabilities that no one 
design can satisfy all needs. I was hav- 
ing a hard time coming up with a func- 
tional design for a robot to assist every 
type of disability. 

Shortly after this initial design, I 
got to talking with a delightful 98-year- 
old lady who knew of my robotics back- 
ground. Myra was living independently, 
but had to have a housekeeper come to 
her home daily to help her with a few 
basic needs. Her mind was sharp, as 
she kept track of her stock portfolio 
and was a great conversationalist, but 
found she needed basic help in moving 
and doing things around her home. 

After a particularly difficult morn- 
ing, I happened to go by her home for 
a visit. "Tom," she asked me, "I wish 
you could build a robot that could help 
me live day-to-day without having to 

SERVO 07.2006 

have a person coming by all the time to 
help me do the simplest things that I 
used to do for myself. I don't want a 
person hanging around me and going 
through all my things." 

A Personal Assistant 
Robot for the Elderly 

Myra passed away just short of 
100 years old, but I thought about her 
desire for a long time. I dug out the 
data I compiled a dozen years ago 
when I was part of a panel that was 
tasked to determine just what people 
wanted in a home robot. Much of the 
information also applied to a robot to 
care for the elderly, but the basic form 
of the robot turned out to be entirely 
different. I soon discovered that a 
robot to assist the elderly could be a 
single design that would pretty much 
cover many of the needs of all seniors. 

The elderly generally have all their 
motor functions. These functions just 
don't work as well as they did in the 
past. They can reach out to grasp some- 
thing, but it may be painful and with 
limited grasping ability. They can get 
out of and into a chair, but that task 
may be difficult. We've all joked about 
the advertisement that shows an elder- 
ly person calling out, "Help, I've fallen 
and can't get up," into a Life Alert pen- 
dant, but many elderly people have lain 
upon a floor for hours until help arrived. 
I have used the term Personal Assistant 
Robot for years to describe a robot that 
can actually physically assist a person, 
not just a "go-and-fetch" machine or a 

80 SERVO 07.2006 

mechanized conversationalist. 

In 1995, I visited an upper-scale 
nursing care facility in Long Beach, CA, 
and spoke with 47 patients with all 
levels of assistive needs. As I expected, 
there were some (14%) who were 
pretty much against having a "mechan- 
ical servant" in their home, even if they 
could return to their homes. I can 
understand this reaction, seeing as how 
it is so new and unknown. It was the 
completely bed-ridden patients who 
expressed this sentiment more than the 
more mobile and active residents did. 

However, over 68% of those with 
whom I spoke were very enthusiastic 
about having a robot to assist them in 
daily needs. I showed all of them — 12 
men and 35 women — two drawings of 
the robot I had designed and described 
how it worked and how it could help 
them (see Figure 3). I spoke honestly, 
telling them that the robot was not a 
house-cleaning maid, but a constant 
companion at their beck and call. The 
remaining 18% took a "wait-and-see" 
stance. I was told by almost all of the 
patients to, "Hurry up and build this 
thing. We [all seniors] need it now." 

They explicitly stated that they did 
not want a robot that followed them 
around like a lost dog, asking them if 
they'd taken their pills or similar 
reminders. Cordless phones and radio 
pendants for around their necks can 
summon their doctor, the police, or 
other emergency services, and timed 
pill containers with a voice reminder 
can easily keep seniors on their medica- 
tions at a far cheaper cost. What 
they all desired was a robot who could 
physically do something — not just roll 
around and "beep and talk." 

They wanted a robot servant who 
could assist them from the floor after a 
fall. They wanted a robot who could be 
directed to go into the kitchen, take a 
Lean Cuisine beef and broccoli meal out 
of the freezer, place it in the microwave 
oven for six minutes, and bring it to 
them when it was done. They wanted a 
robot who could help them into and out 
of a chair, bed, or even a toilet, safely. 

All of these tasks are pretty hard 
for a robot of today, especially the 
safely part. In researching the FDA 
Code of Federal Regulations under 
part 890, "Physical Medicine Devices" 

it appears that sub part F, "Physical 
Medicine Therapeutic Devices," part 
890.5050, describes a "Daily Activity 
Assist Device" under which personal 
assistant robots might have to conform 
for safety reasons. 

Not surprisingly, many of the 
seniors whom I spoke with wanted the 
robot to clean the house, though I had 
mentioned that the robot I had 
designed was not a maid. They had no 
idea just how difficult house cleaning 
is - thorough house cleaning. The 
l-Robot Roomba and Scooba do a fairly 
good job of daily carpet and floor 
cleaning, but dirt and dust does not 
just accumulate on the floors. It is 
deposited upon furniture, walls, and all 
over kitchens and bathrooms. No 
doubt that some of these seniors have 
since purchased a Roomba. 

A competent maid can spend an 
hour a week doing a far better job of 
cleaning a home than any robot, and 
he or she can also bring in a week's 
load of groceries and place them in 
cabinets, refrigerators, and freezers, 
oriented so that a robot can read the 
barcodes and retrieve them (with a 
bar-code or RFID reader in the robot's 
claw). I shudder at the thought of a 
robot set loose in an elderly person's 
home trying to dust a shelf covered 
with many crystal and ceramic 
figurines. At maybe $50-$100 a week 
for simple house cleaning and food 
arrangement — depending on the 
home's size — a senior can pretty much 
live independently with a well-designed 
and functional personal assistant robot. 

Let a person do these low-paying 
tasks for an hour or two a week and let 
the robot assist a person the other 166 
hours. This is certainly less expensive 
than a daily, full-time caregiver in the 
home at a cost of $1 50 to $200 a day, 
or $55,000 to $73,000 a year. A nurs- 
ing home can be significantly higher. 

Personal Assistant 
Robot Configuration 

Not surprising for people who 
know me, my design uses two SCARA 
arms that ride up and down on two 
tracks on each side of the robot. They 
are leadscrew-driven (actually — recircu- 
lating ballscrews for efficiency) and can 

lift close to 200 pounds each, 
much like we would move 
our arms about on the top of 
a chest that is as tall as our 
upper chest. 

SCARA configuration 
robot arms have all vertical 
axes and operate in a horizon- 
tal plane and take little power 
to move a payload back and 
forth, just as a fingertip can 
move a heavy door back and 
forth. SCARA configurations 
offer great lifting power, but have a 
problem reaching up into or down in 
cavities to retrieve objects without the 
addition of special end effectors at the 
end of the arms. Most industrial SCARA 
robot arms have a special end-effector 
that moves up and down for precision 
parts insertion and similar applications. 

Most designers of personal robots 
to assist the elderly have used the typi- 
cal human arm configuration — a mod- 
ified version of the industrial robot's 
"revolute configuration." The shoulder 
joint is at the top of the robot's chest 
structure with a lower elbow connected 
to a forearm and "hand." This type of 
arm can easily reach down into a cavity 
and still reach up over the robot's head, 
but requires a greater amount of power 
to accomplish a lifting task. I wrote 
more extensively about personal robot 
design in the April '06 issue of SERVO. 

Another design issue was the 
robot's ability to keep from tipping 
over while handling a human being. 
Extendible "feet" seemed to partially 
solve this problem. Many other hurdles 
must be met, such as reliable speech 
understanding, sophisticated software 
to make sense of a series of verbal 
commands, useful vision systems, and 
many other design problems. 

How much would such a robot 
cost? As with anything new, the costs 
will probably be far higher that any 
designer ever imagined. Just as the first 
cell phones were as big as a brick and 
cost several thousand dollars, they are 
now almost invisible and are "given 
away" with your wireless phone 
service. The first personal assistant 
robots will probably be heavier than 
we'd like and cost less than a 
Mercedes, but more than a Chevy. 
Using as many "off-the-shelf" items as I 

Figure 7. Care-O-Bot 

could, I soon realized that basic metal 
forming, machining, circuit board pop- 
ulating and soldering, plus assembly of 
complex mechanisms quickly brought 
the cost of initial robots skyward. 

As with any complex design 
project, prototypes must be built, trials 
run, issues addressed, and government 
regulations covered. The final product 
must be engineered, manufactured, 
marketed, and delivered. When I first 
moved up to the Seattle, WA area, I 
met a man who was quite interested in 
providing the large amount of venture 
capital necessary to get the personal 
assistant robot project underway. After 
the " crash" and its devastat- 
ing effect on new tech start-ups, he 
had to drop out of the funding after 
another firm ate his funds. I have 
temporarily shelved the project, though 
I am constantly asked about its status. 

Joe Engelberger 
Changes His Focus 
on Robotics 

Stepping aside from my own design 
ideas, I'd like to talk about other person- 
al robots that are making their way into 
our homes. Joe Engelberger — world- 
renown as the "Father of Industrial 
Robotics" — has changed his focus in 
the last decade from factory robots to 
robots who care for the elderly. Shown 
next to his successful HelpMate robot 
designed for hospitals (Figure 4), Joe is 
pushing close to 81 years old himself. 

I had the privilege to eat a quick 
lunch with Joe back in 1984 at the 
International Personal Robot Congress 
in Albuquerque, NM — one of the first 
personal robot symposiums. Joe was 
already thinking ahead of a robot for 

the home, long before his HelpMate hit 
the hospital floors. 

He clearly sees the need for a robot 
in the homes of our seniors. In several 
interviews with TV and magazine 
people, he has said that his "HomeMate 
will fetch and carry, cook and clean, and 
help with all the activities of daily living 
for a fraction of the cost of skyrocketing 
nursing home or in-home care; leasing 
at $1 an hour, or $600 a month." 

Figure 5 is a CAD drawing of his 
proposed HomeMate robot. "The 
robot will have thick skin," he chuckled. 
"With an 85-year-old person, the robot 
will have to react to four or five 
questions: 'What is lunch?' 'Where is 
it?' It's very easy to sense distress. It 
can go up and say, 'Tell me about your 
high school reunion party,' and the 
robot is going to clap every time." 
Engelberger had proposed the creation 
of a company called RoboCare, Inc. 
(not to be confused by the Italian 
consortium of the same name), to 
design and produce his robot. Quite 
frankly, if anyone can do it, Joe can. 

To be expected, US companies 
are not the only firms interested in 

Figure 8. RI-MAN holding a 
full-sized human doll. 

SERVO 07.2006 



Figure 10. Sogang 
University robot. 

a robot to 
assist the eld- 
erly in inde- 
I PA, of 

Stuttgart, Germany has produced two 
demonstrator platforms of a robotic 
home assistant called Care-O-Bot. The 
first model — Care-O-Bot I — was 
strictly a mobile platform for research 
purposes. It had a touch LCD screen for 
basic input/output information. The 
Care-O-Bot II model is equipped with 
adjustable walking supporters to assist 
a person when walking behind the 
robot. The robot also has a fairly sophis- 
ticated manipulator arm attached. 

Figure 6 shows the Care-O-Bot II 
with its amazing manipulator arm. It 
can navigate autonomously in indoor 
environments and the manipulator 
can be programmed for various pick- 
and-place tasks. The control software 
of the Care-O-Bot II operates on two 
industrial PCs and a separate hand-held 
control can be used for remote 
programming and operations. 

Autonomous functions can oper- 
ate the manipulator arm, allow roving 
about a home, utilize images from a 
camera and laser scanner in the head, 

and be controlled by voice commands 
or computer keyboard inputs. Figure 7 
shows the manipulator in use. 

At an automation fair in Germany 
in 2002, the Care-O-Bot II actually was 
programmed to approach visitors and 
hand out business cards. The robot 
then asked the visitor for his or her busi- 
ness card and placed them in a tray. 

It goes without saying that the 
greatest interest in robots and the home 
of the largest robot manufacturers is in 
Asia — in particular Japan and Korea. 
From Sony's Aibo to Honda's Asimo, the 
latest advances in personal robotics has 
come from Japan. Though Sony has 
recently bowed out of the field, many 
new products are arising from these 
countries. It is estimated by the Japan 
Robot Association that over 16,000 
"service robots" — the term for non- 
industrial, but also not entertainment 
robots — are in place, with the majority 
in hospitals and nursing homes. 

Japan and Korea are facing a 
greater percentage of elders and a 
subsequent greater need for care. The 
RIKEN-Bio-Mimetic Control Research 
Center in Nagoya, Japan has developed 
Rl-Man — an anthropomorphic (man 
formed) robot to be used as an elder 
care robot. Figure 8 shows the RI-MAN 
carrying a human-sized doll, weighing 

only 26 pounds though. At 5' 2" tall, the 
200-pound robot is expected to carry 70 
KG — over 150 pounds — in the near 
future. Covered with a pliable, soft foam 
rubber skin, it is expected to be people- 
friendly. Figure 9 shows two of the 
robot's joints and an overall schematic. 

Researchers at Sogang University 
recently developed a robot to assist 
disabled and elderly people with basic 
mobility. Figure 10 shows how a person 
is attached to the robot's arms at their 
waist, and the machine slowly leads the 
person about a room. Japan's Waseda 
University has long led the world in 
specialized robot development, but MIT 
in the US with its COG and KISMET per- 
sonal robots is not to be left out of the 
game. Carnegie Mellon and other US 
universities always manage to keep us 
amazed with some very unique robots. 

I have only touched upon a few of 
the new robots designed to care for 
people. There are many US companies 
and private researchers developing new 
machines. Interest in robots for the 
home is experiencing a tremendous rise. 
The movie Bicentennial Man and similar 
films have shown robots in the homes of 
average citizens. Non-tech people are 
scooping up Roombas and Scoobas. 

There are always the "early 
adapters" who will buy some seeming- 
ly useful gadget just to be the "first 
person on the block" with something 
new. Most people are the "middle and 
late adapters" who want a new tech- 
nology to prove itself before they buy. 
Early adapters "pay the price" and help 
the companies weed out the kinks and 
problems before the masses move in to 
buy. Home care robots for the elderly 
will soon be at the marketplace. 

Advertiser Index 

All Electronics Corp 25,35 Industrial Ventures 66 

Critical Velocity 35 Jameco Robot Store 2 

CrustCrawler ....9 Lernos International Co., Inc 13 

Dimension Engineering 22 

DynoMotion 35 

Futurlec 35 

Future Robotics 63 

Garage Technologies 35 

Hitec 3 

Hobby Engineering 

Lorax Works 25 

Lynxmotion, Inc 23 

Madell Technology Corporation 35 

Maxbotix 35 

Medonis Engineering 35 

MeerKat Systems, Inc 35 

Net Media 83 

82 SERVO 07.2006 

Parallax, Inc Back Cover 

PCB Fab Express 63 

Pololu Robotics & Electronics 56 

Robot Power 56 

Robot Shop 78 

Solarbotics 17 

Solutions Cubed 34 

SpectroTech 35 

Technological Arts 35 

25 Vantec 56 

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What can you do with eight 32-bit processors (COGs) in one chip? Real simultaneous multi-processing! The 
new Propeller chip is the result of our internal design team working for eight years. The Propeller chip was 
designed at the transistor level by schematic using our own tools to prototype the product. The Propeller is 
programmed in both a high-level language, called Spin™, and low-level (assembly) language. With the set 
of pre-built Parallax // objects"for video, mice, keyboards, RF, LCDs, stepper motors and sensors your Propeller 
application is a matter of high-level integration. Propeller represents the first custom all-silicon product 
designed by Parallax. The Propeller is recommended for those with previous microcontroller experience. 

Propeller Chip Specifications 

Power Requirements 

3.3 volts DC 

External Clock Speed 

DC to 80 MHz (4 MHz to 8 MHz with Clock PLL running) 

Internal RC Oscillator 


System Clock Speed 

DC to 80 MHz 

Global RAM/ROM 

64 K bytes; 32K RAM/ 32 K ROM 

Processor RAM 

2 Kbytes each (512 longs) 

RAM/ROM Organization 

32 bits (4 bytes or 1 long) 

I/O Pins 


Current Source/Sink per I/O 

50 mA 

Propeller users have already been hard at work developing Objects for the Propeller Object Library and discussing 
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Propeller Chips 

P8X32A-D40 (40-Pin DIP) Chip 

P8X32A-Q44 (44-Pin QFP) Chip 

P8X32A-M44 (44-Pin QFN) Chip 

Propeller Tools 

Propeller Demo Board 

PropSTICK Kit 

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To order online visit To order by telephone call the Parallax Sales Department 
toll-free at 888-512-1024 (Monday-Friday, 7 a.m. to 5 p.m., Pacific Time).